I agree with pocoellie - What you describe sounds like the way to go. This way any uneven matching is hidden by the center circle.
How are you handling the center circle? Eleanor Burns has a method that uses fusible interfacing. You put the circle fabric on the bumpy side of the interfacing, sew totally around the edge. Then carefully cut a slit in the interfacing and pull the fabric through. Use a pointy thing to smooth the seam. This way you have a perfectly turned center circle that you can fuse to the wedges of your "plate"
If you are worried about the fusible messing up the ironing board where there is a hole in the wedge, place a piece of freezer paper in the gap. It will peel off when cooled. Then you can use that to help place the completed wedge on your background fabric.