A couple of corrections - I guess if I'm using charcoal in the medium, I can't call it inorganic. But I do want one that will not be bio-degradable.
I also have one photo, of the structure still in the form. Only the front surface is visible, although it's obvious that the entire piece is 5" thick. The front surface is about 5/8" (15 mm) thick, then buried inside are two sheets of 2" styrofoam, and the back surface is at the very bottom, about 1/2" thick. The pink circles are the blockouts for the holes for the net pots. I originally made mostly 2" circles, but I've since had to enlarge them to 3" after I saw how tiny the 2" net pots really were.
The tree branch is there for decoration only, I'm not planning to mount any of the orchids. The dumbbell is pressing down on an unruly twig to embed it in the surface.