I played around with the concept of the one made by M*QC. I don't have the circle ruler but I cut mine out using my Olfa Circle Cutter. I drew a circle on my squares of fabric and layered a piece of batting (W&N) the same size as my square and sewed them all together. Cut them out and turned them right side out. There was so much bulk to sew with the batting in it. When you turn the curves down and go to sew them, you will be sewing 4 layers of fabric and 2 layers of batting. I couldn't get it to lay nice and match up like I wanted it to. I am going to do my Cathedral Window quilt the "old fashion" way where you make the circle and then place a square of the focal fabric in the center and then sew the curves down to secure it.
i did make a table topper for July 4th doing it the way Jenny does and it turned out alright.