It's rare for two flemish string makers to make their strings exactly alike--different size fingers twist differently--so it won't help much to know what the other guy does.
What I'd try is this: Cut the bundles way longer than you think you need. Make the first loop working from the end towards the middle (that's how I make mine anyway). Keep in mind the loop is going to stretch. After you get the twists in for the first loop, but before splicing the bundles to make the loop, measure what you have left. That should tell you how much it took to make the first loop, which will let you know where to start the second. Take lots of notes. Measure everything. Might take a few tries, but that should work.
Personally, I think this a rare occassion where an endless string will work better. I can't remember if I made a flemish string for a bow with siyahs before, or almost did, but if I recall correctly it wasn't practical.