This is the hard part to explain, and I'm going to do the best I can. If this doesn't help you, then just go to google and search for other web pages about making flemish strings. After reading a few of them, surely somebody will explain it in a way that's clear to you. If not, then just take my advice I gave on page one and just do it.
The first thing I want to explain is this really cool property that fibers have that makes them want to become string or rope and hold together. Let's say you've got a bundle of strands that you're holding between your fingers.
With your right hand, you begin to twist the bundle away from you between your fingers.
The tighter you twist, the more the bundle will want to form a kink. Let's say you let it. Just move your hands toward each other, making the twisted bundle a little slack, and look what happens.
Do you see that? The bundle will naturally start twisting around itself. Look careful at the directly it's twisting, though. Notice that it's twisting in the opposite direction from the direction you twisted it. That's important. The moral of the story is that if you are going to make a two-bundle string, you should twist the individual bundles in one direction. Then you should twist the bundles together in the opposite direction. If you twist the individual bundles clockwise, then the bundles should be twisted together counter-clockwise. By twisting the individual bundles, the two bundles will want to twist against each other. That's what holds the string together. Isn't that wonderful?
Okay, with that wonderful news, let's start twisting the string. The first thing you have to do is put the two bundles together and measure about 7" from the end.
7" is just a guideline. Every string jig is a little different. If your string turns out to be too long, then try 7-1/4" next time. This jig is designed for a longbow. Longbow strings are usually 3" shorter than the bow length, whereas on recurves, it's more like 4" shorter than the bow length. So if you're making the string for a recurve, use 7-1/2" instead of 7". After making a few strings, you'll get a feel for where to measure it.
Now here's how I do my twisting. I hold both bundles in my left hand and twist with my right. Each time I do a twist, I inch my left hand up a little. Here's some pictures showing the procedure I use.
In this first, picture, I'm twisting the red bundle between the fingers on my right hand. The direction of my twist is away from me. If you were standing to my right looking toward the string, I would be twisting clockwise.
In this next picture, I have twisted my hand over and grabbed the brown bundle with my other two fingers.
Then, I hold both bundles and twist my hand back so that the red bundle goes over and toward me. The brown bundle goes under and away from me. If you were standing to my right looking toward the string, I would be twisting the red and brown bundles together in a counter-clockwise direction.
When I twist the bundles together like that, I try to hold them both and apply the same tension to both. That way, they'll twist evently. I don't want one bundle to be straight while the other is wrapped around it. I want them both to be even.
Starting with this next picture, I'm doing the same thing. I'm twisting the brown bundle just as I originally twisted the red bundle.
And now I'm doing the same thing as before...
...and blah blah blah.
It all makes sense now, doesn't it? If not, just look carefully at my hands, and you should be able to tell the direction I'm twisting. If it isn't clear, have a look-see at the video clip of me twisting the string.
Continue doing this until you've got a little length twisted together.
Then fold it in half to see how big the loop will be. Twist a little more if you need to, or untwist a little until you get the loop to the size you want. Once you get the loop to the size you want, then put the red strand with the red and the brown with the brown and smooth them into each other by squeezing it between your fingers, and sliding your fingers down..
This works better if you have lots of wax, which is why I had you wax the 18" earlier, but you can add some wax at this point, too, if you want.
Hold the loop in your left hand, and twist with your right hand exactly as you did before, in the same direction and everything.
Twist until you get all the loose ends twisted, and then twist for another half inch or so. Then put a twisty tie on there to keep it from unraveling while you work on the other end.
Before doing the other end, there's something you should be aware of. While you're twisting with your right hand, everything on the other side of your hand gets twisted in the opposite direction. Unless you undo that twist, the string will have a hard time staying together. So here's what you do. First, put the loop you just made on a nail (I use one of the nails on my jig).
Stretch one strand out, and twist from the end. The twist would be clockwise if you are standing at the end facing the loop on the nail. I do it by rolling it in my hands, because it's quicker. The top hand goes in the direction shown.
When you do the other loop, the same thing is going to happen, so it isn't enough to merely get all the counter-twist out. You have to add extra twist to it. Doing so will help the string stay together in the end.
Do the same thing to the other bundle.
At this point, you have a decision to make. You can either make another flemish loop on the other end, or you can use a timber hitch on the other end. There are some advantages to using a timber hitch.
1. If you do another flemish loop, you run the risk of having one bundle longer than the other, which will put tension on one bundle, but not on the other, which will make the string weaker. You don't have that problem with a timber hitch.
2. Timber hitches are easier.
3. Timber hitches are more adjustable.
But there are also some disadvantage to using a timber hitch.
1. Timber hitches can slip a little
2. You'll have a dangly little string hanging off the end of the bow that will attract cats.
3. After repeated adjusting of a timber hitch, the string there begins to get a little ragged.
Personally, I don't like timber hitches, but I use one on my tillering string, because I found it very useful for adjusting the length. With one string, I can tiller with a long string, a low brace, and a full brace.
If you're going to use a timber hitch, you might also like to measure out the string a little longer than you would if you are doing a doubled ended flemish twist. So, for example, if you were making a string for a 66" bow, you might want to measure it at 68" or 70" on your string jig. Or better yet, don't use a string jig at all, since with a timber hitch, you don't need your measurements to be quite so precise.
I use a timber hitch on my tillering string. Here's a look at my tillering string showing how I tie a timber hitch.
Now let's suppose you want to do another flemish loop. You have to be extra careful when doing the flemish loop that you have the two bundles pulled exactly the same so that one isn't sagging. If one sags, then the string will be weaker, because all the load will have to be carried by the other bundle. You want to evenly distribute the load by preventing any sag. To do that, hold one loop up and sort of comb everything down to the end. If there are any little loops or sags anywhere along the way, comb them out. I always comb out the individual bundles as I take them off the string jig, so all I have to do is stick my fingers between the bundles and run them down to the end.
Once I've got them all combed out, then I start back up at the loop end and smooth the whole thing down by grabbing it with my hand and sliding my hand down.
Now measure it off 7" or so just as you did before.
Notice that in this picture, the brown bundle is a little longer than the red bundle. If that happens to you, don't worry about it. The only way to correct it is by causing one of the bundles to sag. It's better that one bundle be slightly longer than the other than to have one bundle sag. If there's a huge difference (which isn't likely if you use a string jig), then just trim one of them to match the other.
Now twist it exactly like you did the first loop.
The temptation is to want to do the mirror image of what you did on the first loop. That's what I did on my first try, and the whole string unraveled on me. Just do exactly the same thing you did on the first loop and in the same direction.
While you're twisting the second loop, you'll get some counter twist on the other side of your hand, which will make it difficult to twist unless you unravel it every now and then. I unravel it by sticking my hand between the bundles, spreading them apart, and gliding my hand down.
The twisty tie keeps the other loop from coming undone.
Continue twisting until you have all the ends twisted into the string, and then twist for another half inch just like before. Then put a twisty on that end, too.
Now put your thumbs in the loops and stretch it out. Apply some tension, but not so much it comes apart on you.
If one bundle was a little more saggy than the other, this will help. If it's visibly saggy, then you ought to redo the loop.
Once you have it stretched and all the sag out of it, begin twisting it while holding it stretched out. Look carefully at the direction of the twist on both ends so you'll know which way to twist. If you can't figure it out, then start twisting anyway. You'll soon figure out whether you're going in the right direction or not.
Some people like to count the number of turns they put in it. I don't do that. Just twist until it looks about like other flemish strings you've seen. Here's what mine looks like.
Now try it on the bow. If the brace height is too high, take the string off and untwist it a little. If the brace height is too low, take the string off and twist it a little tighter. Then try again. Once you get it about right, pull the bow to full draw a few times. This will help get any stretch out of the string. Check the brace height again and adjust as necessary. Some people (e.g. John Scifres) like to stretch the string by hanging weights from it and leaving it over night. Do whatever your heart tells you.
If the string comes out so short or so long that you can't twist it or untwist it enough to fix it, then unravel one loop and redo it.
You'll noticed after doing your first string whether you need to make any adjustments on your jig or not. You don't have to change anything on the jig, but if the string comes out too short, then the next time you make a string, start twisting 6-1/2" from the end instead of 7". Or use 68" instead of 66" for a 66" bow. After the second string, you'll figure out what you need to do, and it'll be a cinch from then on out.