Here's a picture of the pot assembly. Wave petunias per pot from the top: 1, 2, 3 & 4 in the bottom. I also like to put bacopa in between the petunia plants.
The little boards are about 2" wide and 8" long. Since the pots are just thin plastic nursery pots, the plastic is a bit thin. If you used a stronger pot, you probably don't need the boards
