I ran three gathering stitches across the edge as evenly as possible, but more importantly, made each row of stitches stitches as close as possible to being directly underneath the one above it. I'll most likely sew them down by machine.
I already did the back, but it wasn't quite as well-planned. Well actually, I did one edge and then decided to make that one the back since I figured my second try would be better! There's not actually a pattern difference between the front and back.
I was a bit concerned about how I'd show a picture of this, given that it's pale pink top-stitching thread gathering white fabric, which makes a well-defined image difficult. Just upping the contrast was not cutting it, so I ended up using the deconvolution filter in the G'MIC Gimp plug-in. Very useful.