In Arizona when we ran trail rides all the lead horses ground-tied because we often had to get off and adjust a girth or pick up a water bottle and the trails were narrow enough in some areas that you couldn't lead your horse back along the string.
The cowboys ground-tied by dropping the reins but they used split reins so the horse wasn't going to step through the reins and get caught although they could still step on one and yank their mouth. I taught my pony to "Stay" like a dog and just left the reins in the normal position. I suppose you could also teach the "Stand on the Mat" exercise and take a small, bright, piece of plastic along as a mat? Hanging the reins over an ear works for me too! Cherie