These days, besides modern style endless strings, Koreans use a fancy knot tied into an endless unserved string, with FF. They seem to have done the same with silk in the past. I've also used this knot, the korean knot has been very difficult to get right for me, compared to this one. (drawing by Bede from ATARNnet)
edit: the below is more of a Manchu than a Korean knot. I should make an illustration of the Korean knot...
can also do an overhand or fig 8 on a bight, but that's very difficult/impossible to adjust
FF is so ridiculously strong, it doesn't matter that knots create a weak point. With lighter bows, it's not difficult to overbuild a dacron string either
Not necessary with dacron but with FF, I burn the tag end to prevent it slipping through the knot, and haven't had any problems with my 50# bow, shooting 7gpp. I used to use CA glue to secure the knot, too, but that makes it make a loud noise when it slams into the string bridge