I just did this block yesterday for the DJ. The way I did it was to sew the white side pieces together from the points to the corners, then I took the pattern for those pieces and cut away the seam allowance on the curve, put it onto the back of the piece and ironed back the curve seam allowance on all four sides. From the front then it looks like a window. Then I cut a piece of the yellow fabric and from the back I put a small bead of Elmer's school glue onto the very edge of the curves all around the window. I placed the yellow face down and ironed the glue in place. Then the yellow was exactly in place. I was able then to separate the seam and sew right on the folded line on each curve. It came out perfect.