I have made these two different ways.
1. With 3 fabrics. One with a nice print for the corners, one that matched very well for the 4 side pieces and then much less fabric for the 1 center square.
2. With 2 fabrics. One with a nice print for the corners and then a coordinating color for the 4 sides and one center.
When the D9P block is finished, no matter which kind I made, the center square was cut into four pieces and then the side pieces looked like strips "framing" the corner pieces.
I hope that answered your question. When the quilt top is finished, all your corner pieces were framed with the other pieces and the other pieces made a look similar to a link chain. It's a pretty cool effect.