However, I did not have the time or the motivation to deal with an involved pattern for a suitable edging.
What I did was this. I took my trusty steel crochet hook (7, I believe), and poked and crocheted a simple row of single crochet all around the edge. This was Row 1. I did make sure to count how many I had on the first side, which was very smart of me and really surprised me (grin).
Then, I made a very simple, gentle ruffle by doing a Ch 2 and then 3 HDC in one SC, ch 1, 3 HDC in the next, and so on, with an extra 3 HDC in each corner.
This was quick, it was easy, and it looks sweet and uncomplicated. The point is that not everything must be complicated; simple can be nice, too. I'll post a photo after the person I'm sending it to gets her chance to see it first.