Sand... putty... sand... paint... sand... putty... sand....
Cardboard template for lower block.
Parts cut & kerfed. I'm using 1/2 inch foam board, not 3/4 which I may have wrongly said above.
Backbone epoxied on. I haven't entirely figured out the mounting approach for the lower block, but I have a good idea on a way to do it that will be a no-tools removal/installation.