TAA DAA! I made the right side removable!
At each corner "plug in pin blocks" (wood craft beads with dowel in one and a corresponding hole in its mate) were glued on. Lift the side to remove, plug in to install.
I knew it wouldn't be long before the blocks broke off from use so I drilled tiny holes from the outside through the blocks, screwed in tiny screws, and drilled out any screw parts that blocked the holes with my Dremel tool. I then filled in and painted the screw holes on the outside. All extra work but worth it for the strength.
With the removable side temporarily in place I glued the rest of the shell to the base.
Here are more views of the inserts in place. MUCH easier to get at things on any level when any inserts above it are removed.
While searching for treasure, a couple of thugs move a fallen cupboard out of the way and discover a large hidden hole in the floor. Wonder where it leads? "I ain't goin' in there! YOU go first!" "No way, pal! YOU go first!"
NEXT: Terrain and what I learned