So a while back I wanted to make a keyboard with a slightly custom layout, somewhere between the Happy Hacker keyboard and the NCR80 kit. I sent out the files to be farmed out by Xometry, and it was pretty cheap to bump it up from 1 set (top and bottom) to three. I've actually been using number 1 as my daily driver, with just some sticks of oiled red oak as the spacers between the aluminum. Number 2 had 3D printed left and right spacers, with some springs for the middle.
Now for number three I actually designed and printed a "proper" case. In the pic you can see where there's some glue drying because I overestimated the tolerances on my Ender3 clone, but it split along the layer lines so some super glue, sandpaper, and a coat of spray paint (I'm going to go with "Bauhaus Yellow") should fix it right up.
The top plate slides into a groove in the case (which needed to be looser, hence the repair job). The bottom plate goes into a rabbet in the bottom. There are slots for captive nuts so the screws won't show through the top. I also printed some wedge-shaped feet that run the front-to-back length of the bottom plate and give it about a 6-degree incline.
The design is pretty run of the mill, but it the direct inspiration was the keyboard for the Atari XE Game System, which was my first proper computer, even if I didn't have a disk drive.