I wanted a case for my Rpi 3 that was slim and offered space to mount a stand 5V Rpi fan. I found a case that was slim but there was no way to mount a fan so I remixed it! I use the Pi to run Octoprint.
Simply super the glue the fan on with a few dots of glue. Make sure its facing the right way so the air flows the right way.
If you use slightly smaller M3 bolts there is even room for 3mm magnets to be glued into the holes on the bottom of the case that allows the Pi to get mounted ANYWHERE on your CR-10 or metal control box. I plan on using the magnets to mount the Pi easily on an enclosure later.