At this point in time, I only will make my pants out of handkerchief weight linen or very light weight (and breathable) cotton block printed fabric. Because I do not want to fight with drawstrings or sashes in a port-a-john in the dark, I only use elastic to hold them up. Elastic, however, can be bulky and some of the wide waistband types of elastic can be quite hot during exceedingly humid Pennsics. After testing out a few different options, I have found a remarkably comfortable way to finish the waists of my Pennsic pants.
I need to add that the actual pattern I use for my pants is Uncle Rashid's Salwar pattern. One can make these as loose and billowy as one cares too and it is also not necessary to construct them with a low crotch (as some people prefer to prevent chafing by opting for a higher placement of the crotch). When worn with Ottoman or Persian coats, no one will ever see the crotch OR the waistband, so this is an area where comfort can safely dictate construction. (Note that while I am referring to a specific pattern here, I can apply this waist treatment to any pair of pants that is cut using rectangular construction methods.)
When laying our my pattern, I add extra length to the top of the pants, usually a couple of inches. I sew the legs of the pants and then sew them together and finish off the hem of the cuffs. I then begin my waist treatment by folding the top edge in approximately a half an inch. I either press it with an iron or run a basting stitch to secure it.
I then fold it in again another two inches, pin it in place, and then sew along the bottom (leaving a small opening at the front or back seam of the pants to insert elastic later). I then sew a seam near the top of the waist (1/4" to 3/8" down from the fold) and one more seam between those two (this one will also have an small opening near where the bottom seam is also left open to allow for insertion of the elastic.)