Yep, build yourself a tillering string with a braided loop on one end that's about 74" long. A bowyers knot on the other end will give you all the adjustment you need.
I build Flemish twist strings for all my bow strings. They have a lot more adjustment than a continuous loop string and I just like the softer feel and look of them a LOT better.......more traditional too. You can make a string jig quite easily. Google "Flemish twist string jigs" and you'll fine several. They do not have to be fancy but I built a walnut one with brass pins that's nice to use. A pine board and nails will do.