Been keeping my flag in my back pocket for 47 seasons. Never had it fall out.
The reason folks switched from back pocket to front belt was to reduce the number of incidences that showed up on video when an official - particularly the Line Judge - would reach for his flag in his back pocket, then NOT pull/throw it. Coaches would go berserk on the sidelines, and the coordinators didn't like having to defend such action. I think it started in the NFL, when video tape became prevalent, and everything shows up. Wings started putting their flags at their waists, where the 'reach' is not so noticeable. Now, whether needed or not, that's the fashion. Not sayin' it's bad - or good - just a fact. (Guess I'm just not fashionable.)
I thought all flags came with a balled end, these days. But, if not, yes, draw the flag tight at the base of the ball and tie it up with a standard beige rubber band. If you have trouble keeping it from falling off your waist, get a seamstress to sew a piece of elastic band on the inside of your waistband, and tuck the flag between the elastic band and the waistband.
Or, put it in your back pocket.
