Because I’m making it with smaller needles and yarn, I’m going to do a few extra rows when the instruction says to knit x rows, and a few less when it says to knit x inches to compensate a bit.

Magic Looping on 47” or so long circs.

knit 10 rounds before purl round of waistband

knit 15 rounds before short row section

followed next size down measurements in inches for how far to knit before doing each short row, but worked the short rows (stitch counts) for the large size (88 sts caston)

the “markers” for gusset are where the sts are divided for magic loop; back is where caston yarn dangles

worked the non-parentheses # of gusset extension stitches

once gusset extension flap was knit, I moved the leg sts just to the left of where the working yarn is to another circular needle. Next I put both sets of 10 sts of the gusset onto DPNs and grafted them together (I had to cut the working yarn at this point).
Then I picked up 11 stitches along the side of the gusset using the newest circular needle (55 sts total for leg) and worked 10 rounds of knit, 6 rounds of seed st (moss st) and bound off with Jenny’s Surprisingly Stretchy Bind off. Then worked the other leg the same way.

I used some 1” fold-over elastic I had on hand (its polyester,nylon,lycra so it won’t interfere with diaper cover functionality and I hand stitched the ends together with plolyester thread) and whipstitched the hem down around the elastic using the tail from the original waistband caston and wove in the end. (It will be simple to get to the waistband to make size adjustments if necessary)

Final resulting measurements are:
15” waist
7” rise in front
7.5” rise in back

I may do some decorative embroidery on them. Fish, pirate ship, palm tree, something like that.