Print the box and the base. The "rings" for the fake connectors are just for cosmetics and completely optional. The motor caps are also optional, I just thought it would be good to keep dust out of the rumble mechanisms. The motor "ring" is a spacer I found I needed to hold two rumble motors in a single clamp. All of the motor parts are sized for 25mm diameter motors, I used Xbox 360 ones.
Only the main box needs to be printed with support.
I printed everything in ABS plastic.
This was designed around the SparkFun RedBoard, not a standard Arduino Uno, so you might have to adjust the sizing and placement of the connector holes if you use another board.
The label is also completely optional, you want to print it onto sticker paper using a program that lets you print images at "actual size" (58mm x 18mm) and at a high DPI.
This is designed to use M3 screws for mounting the board, mostly a couple really short ones (6mm long?) but also one 40-45mm long one to hold the box closed. I screwed up here because I designed this around a 3D model of the Adafruit Motor Shield V2, but then used a cheapo eBay L293 shield in my build. Both shields only have 3 of the 4 holes of the Uno mounting pattern, but the missing hole isn't the same on each board, so I couldn't actually screw my case together. It still stays together fine just friction-fit.
The other minor issue is the spaces for the m# nuts are a bit too tall. I held the nuts in with screws and then filled the gaps with hot glue so they wouldn't fall out during assembly.
Screw the Arduino board down to the base, then attach the motor shield. Run your wiring through the hole in the main box before screwing them into the terminals. Close the box on the base, then connect the power and USB cables. I mounted my box to the pedal base with double-sided foam tape.