Flemish string jigs are not that hard to find designs for online. I have posted my adaptation for one below and pics of it. However, I do not always make Flemish strings. I teach a beginning blow making class where I teach bowyers how to make a string they can use to shoot with and to use during tillering. It is an overbuilt string that will give no worries. The string is also great because it will work on any bow no matter how long or short. If extra string exists you trim it off. Easy.
I call this a full twist string because after making the loop I do reverse twist all the way down and tie it off with an overhand knot. They are brainless to make but can take roughly 15-20 minutes. I make them while watching movies, camping or coaching tillering. I really like these strings. I was taught to make these by a bow maker in southern Illinois and really like them. However, he never taught how he got his diacron measured out. With some experimentation I found that you loose 1/3 of your string length to the twist and was able to make a string jig that accommodates for that. This is the cedar board pictured below. If you need an explanation on anything please let me know. The knot I tie on the lower limb is pretty simple but any knot used by the Native Americans will do.
On the Flemish jig I have the peg holes drilled to make a string appropriate for the size bow marked by the peg. Just follow one rule. start the loops seven inches from the end of the string bundle. There are plenty of places to find descriptions for how to use such a jig and make a string but if you need my effort on that just holler.
BTW I like using the clothes pin to hold the string. I simply glue that in place and go to town.
Happy string making!