This is one of the mods I've given my Ender 3 Pro. I wanted to have a spot for my USB, Micro SD card, SD card, and paint razor (what I like to use to get stuck prints off the bed). I also wanted to label my printers. Thus I made a holder for all the tools with a label, both Alpha and Omega. For this, I simply printed the part with the top on the bed. A more quality setting will define the pocket dimensions better and make the label clearer. Once printed, I just took the two screws out in that corner and pushed the motherboard housing down a bit to slide it in. It is quite a tight fit for no slop, so if it goes in tough, that was by design. Once it is slid back, the little grove allows the motherboard housing to slide back up and get screwed back in. Please let me know if you have any questions.