In all honesty, it would have taken far less time to cut out feet and slimmed the bottom board. However, this does make the bottom and feet out of one solid piece of wood.
I started with a 1/4" spiral bit, then finished with a 1/8" two flute bit. This is the longest carve by far in this project.
The very thin line on the 18" pieces are used as the 8" cut lines. I ran these through my table saw slimming them down until I got to 8" on each side.
The bottom piece I used the edge of the feet as the cut line.
Once the side rebus pieces were at 8" square, I adjusted the blade to 45 degrees and cut the left and right sides of each piece. This I did for simple glued joinery. Once I had my fence set properly, I cut all the pieces at the same position.