While I was building the basic box for module #3, I figured I was going to have enough Gatorfoam left over from #3 to build the basic box for module #4, so I decided to build both of them back-to-back. That way I had all of the tools out, all of the remember-how-to-do-it info fresh in my head, and I'd have a better look at what my layout will look like when it is finished.
All of the boards are edge-glued, so the blue masking tape will stay on for now to hold it all together until I get around to ordering more Gatorfoam and building the interior honeycomb structure.
The creek in the back makes a quick turn back toward what is the front of the layout, so I only needed to make a couple of cut-outs in the vertical boards. The cut-out on the right hasn't been removed yet, as there is no hurry in doing so.