I went to the thrift store looking for soft wool sweaters to turn into longies (wool pants to go over diapers). The great thing about what I was looking for is that often, crappy sweaters from Old Navy end up getting felted when washed, and then donated to a thrift store. Normally, this means sweaters I have to sort through to find the good ones. In this case, it doesn’t matter! In fact, it could be kind of nice, since the fabric would be denser.
I basically winged this pattern, but it turned out great (and took seriously a half hour to make). I found a turtleneck sweater made of wool and mohair. I cut off the turtleneck, and the bottom of the sleeves.1 I guessed at how long to make the legs — I figured extra long isn’t bad for a baby who has long legs to begin with, and who is crawling (and doesn’t need to worry about stepping on her pants). If I had a walking baby, I’d consider tacking up the cuffs, so I could let them down as she grew.
I sewed the two legs together at the crotch, about 3 inches. I then pinned the legs to the top (using the cut end of the legs and the cut end of the turtleneck), making sure the fabric was even all the way around.2 I sewed all the way around the legs/turtleneck.
Lastly, I folded the top of the turtleneck down 3/4″ and sewed almost all the way around it (with a 1/4″ seam allowance) — leaving a small gap so I could thread elastic through. I adjusted the elastic until it was snug enough to keep the pants up but not to snug as to bother, and sewed the ends of the elastic together, then sewed up the gap in the seam.
1 This meant that I was using finished edges at the top and bottom of the pants, and didn’t have to worry about sewing the seams well enough so they didn’t unravel.
2 Since the turtleneck was ribbed and the legs were stockinette stitch, I had to kind of stretch out the top while pinning the legs. It looked a little bunchy and weird, but looked fine once they were sewn up.