Step 1: Hardware
Step 2: Plexiglass
I used a framing square to lay out my lines on the backing sheet of the acrylic. Because the clipboard worked well, and is also roughly the same size as my laptop, I decided to use it as a template for the plexiglass. I used a jigsaw and a straight edge to cut the piece, which worked pretty well. The saw didn't melt the plastic, and there was no chipping. You just need to work slowly and make sure you hold the piece when the blade is nearly through the acrylic. Plexiglass can be brittle when you make very small cuts, so take special care in the corners.
Once the main platform was cut, I cut a handful of small square feet to mount things to the board. I didn't want the standoffs to poke through the other side, and I didn't want any holes in the underside of the platform. I drilled and tap these feet, mounted them to the Arduino board, and glued them down in place. This helped align the feet and standoffs to exactly where they need to be for the Arduino.
Step 3: Standoffs
Unfortunately, these standoffs are made of some very soft metal because a few of them broke off in the holes. You need to make sure that you tap the threads deep enough that the standoffs don't bottom out. If that happens, they will snap off in the hole and you'll have to start over.
I mounted the feet to the Arduino board and made sure they were level. Only 3 of the holes were clear to hold a screw, so I had to make a small support for the other corner that is not secured with a screw. You can use an acrylic cement if you want to special order one, but I used super glue and it worked fine. I have read that the acrylic cement makes clearer joints, but I wasn't making large joints so I didn't care.
Step 4: Finishing the Edges
I forgot to take pictures of this step before the boards were mounted on the Plexiglass. You probably don't want anything mounted to the board until after the edges are melted smooth.
Step 5: Assembly
Step 6: More Arduino?
The mounting holes are a bit different on this board than they are on the longer Mega board. I made some more standoffs for the Uno and mounted it to the Plexiglas alongside the Mega.