I swapped needle size up for the inside to give it an airier look and cast off with a modified crochet bind off.

To do the bind off:
Using a similar sized crochet hook and starting with the last knit stitch ch 3. -Sl st next three live stitches on needle together, ch 3.- Continue - to - around until only 2 stitches are left on the needles. Place hook through the 2 live stitches and around the right side of the last stitch knit (first one worked in bind off row). Catch yarn and draw through as though all loops on hook as though working a slip stitch. Break off and weave in ends.

More chains can be worked to get a more loopy effect rather than a strait edge like I was aiming for. If binding off for a non-circular edge, you might need to do some fiddling to get the gathered stitches to look right at start and/or finish. I haven’t been able to find a tutorial with this particular method yet or I’d link to it.