Finish the Back Edge
After attaching Panel 1, iron the fold-over allowance towards the inside of the corset.
Top stitch along the back edge, just far enough in to create a boning channel. I used 1/4” spring steel to either side of the grommets, so I stitched a little more than 1/4” from the back edge of the corset.
On the back side of the corset, fold the remaining allowance back towards the new seam, hiding the raw edges.
From the outside of the corset, top stitch again. Leave enough room for grommets between the back edge boning channel and this seam. I use medium sized grommets, so I left a 5/8” gap. This put my back edge further to the right than marks on the presser foot plate, so I created a temporary mark with Sharpie. Sharpie is usually removable with rubbing alcohol, but you’ll want to test to make sure before drawing on your machine. Alternatively, you can put down a piece of masking tape and draw on that.
Top stitch again to create a second boning channel.
You should now have a strip for grommets, bordered on both sides with a boning channel.
The image below shows the inside of the corset after the back edge is complete.