It could also be done similar to the rings that bind quilt. Just cut the back circle out of any block you choose. Then layer the batting and white square, quilt the center, place circles back to back, stitch across and fold the resulting curved edges over the white and stitch down. You might want to fold under the edges of the curves before you stitch down. You can also finish the edges of the circles before you layer and quilt by cutting interfacing or material circles and sew to quilt circle, slit and turn to get finished edges before you layer your sandwich. When you get all squares attached together you are completely Done!