A couple of years ago I bought pair of pants a size too big because I knew I could take in the seat. The color was perfect, a gray-lavender. Two years passed. The fabric shrank and faded and I got a little larger. The too-high-in-front waist became annoying enough for me to want to do something about it. After removing the belt loops and the button, I started my cut where the button sat, and tapered it toward the side seams. The waistband lining was shredded by removing so many threads, so I replaced it with bias tape.
Finally, I sewed the belt loops together with a slit for a buttonhole, and put a button tab on the front. The pants are much more comfortable, but they are still faded. See the dark spots where the belt loops were? If the pants had been brand new I don't think I would have been quite so cavalier about chopping here and sewing there, but the change worked, and I have a new sewing trick.
Recently I got angry with a pair of pajama pants. If I bent over and straightened up, there was the sensation that I was losing my drawers. Adding a diamond gusset at the crotch, the most suggested alteration for pants, only added fabric where no extra was needed. Another way to increase the back rise is for paper patterns only. I was not about to remove all the elastic, increase the scoop in back and add to the sides -- in essence, remaking the pajama pants. I wanted a fix and I wanted it fast.
I cut horizontally from side seam to side seam about an inch below the elastic. At that point, the worst that could happen was that I'd lose a pair of pj pants that I didn't like anyway. I sewed a rectangle of flannel to the upper edge, then tried on the pants and pinned loose edges together. At the side seams, I needed no extra fabric, but the center back seam required 2 inches. I ended up with a back addition that looks a bit like a grin, or a semi circle. My pajama pants are now comfortable.
This works for any elastic backed pants where the waistband is not a separate piece. I've done it on pull on jeans, and a dressier pair of pants, mulberry corduroys with a velveteen insert. As long as I match colors, the addition looks like a pattern detail and not like the salvage effort it is.
