That completes the concealed seams, and now all that's left are the leg holes. Since they're still unsewn at this step, take the garment to the right side through one the leg holes.
Our next objective is to sew these leg holes, and there's a few different ways you can do this. Feel free to choose any of them!
1. If you have a coverstitch machine, you can sew in the elastic and finish your foldover seam all in one step.
2. Break up the process into two steps. First, attach elastic to the leg holes on the lining side. Then, flip over the seam to hide the elastic, and use a zig zag stitch to sew the leg hole down and cover up that elastic. You will want your zig zag stitch to be tight so it can stretch, and wide enough to cover the width of the elastic; this helps the seam lay flat.
You DO want to stretch the elastic for this step. A 1-3% seam reduction is ideal but this is up to personal preference. You can accomplish this by measuring, or you can eye it while you sew. This should be just a slight pull, not quite enough to create significant bunching, unless you want it that way. The amount you pull will determine the grip on the leg holes, so you're more than welcome to stretch as much or as little as you want to achieve the amount of security you're going for.
However you get there, that is the last step for the Gabby Bottoms!