Thanks everyone! I tried a modified version (no flange) by sewing the 1" strip on with a 1/2" seam allowance, then pressed it back over itself (so its second raw edge lined up with the original border edge) and then sewed my second border on with a normal 1/4" seam allowance. It worked, although I couldn't figure out a good way to sew the mitres at the corners, and will go back later to hand sew those.
QuiltE - the thing I am working on is a "use up the orphanned blocks" project about which I have very mixed feelings. I am hoping someone at my next craft fair will love it...The pinwheel blocks are from "Vivacious Curvy Quilts" by Dianne Hire. The setting is my own.
[ATTACH=CONFIG]409126[/ATTACH][ATTACH=CONFIG]409127[/ATTACH]
Alison