This is different... we had a thread a while ago about the quilt where you sew two circles right sides together, cut a slit and turn them right sides out and then sew them together on the straight edges of the inscribed square. Then you press open those little semicircular pieces and stitch them down. I made a Nine patch (it's actually more a five-patch, technically speaking!) and lined it with muslin and interlined it with flannel. It's fun because when you are done, it's DONE.
I could also fold in those outside edges for a straight edge to the quilt.