Here are some directions for a 2 bundle Flemish string. You don't need a jig but they are handy and I use one.
2 different colored spools make it easier. I use B 50.
Measure your ntn distance. I add 12 inches to that. You'll have to experiment with that value and add or subtract some.
The first string of each bundle is the full ntn distance + the 12 inches or so. Step down each successive string by 1 inch resulting in a 1/2 inch difference on either end.
I tie 7 strings per bundle. Wax them and twist'em. No way I can describe the Flemish twist..sounds like a song...and the subsequent serving process. Lots of You Tube videos around though.
BTW I start the loop twist at 9 inches per loop. I tie a double loop string. You can make the loops to fit your nocks. Make the bottom loop tight enough to stay on the nock.
After tying the first loop put a twist tie around it or it unravel when you tie the second; remove all other twists.
A good Flemish string has 1-3 twists per inch and one is better than 3.
Jawge