Step 7: Finish the Body
Topstitch closed. Stitch the same distance from the edge as you did when closing the gap earlier, so your stitching will go right on top of that stitching. You could whip stitch or slip stitch by hand if you prefer, but I don't think it's as secure.
(In these pictures the strap isn't attached yet; I then found out you have to have the side open to stitch the strap on, so I had to rip out my stitching and redo it after adding the strap. And that's why you shouldn't start a project the night before an event.)