How big of a box do you need?
I use these boxes for a lot of projects
click select country, see if Bavaria is supported.
Small box was used for a remote control, with hole cut out for the keypad, larger box used for score display with drill holes only for screws to hold boards.
If you don't want screw holes showing on the top of the box, get some threaded nylon standoffs and glue them on the inside of the box. Glue will depend on what two surfaces you are gluing to. You will have to cut the standoffs to the height you need.
I tend to use these type of switches when I do something like this:
If you have them available locally.
One tip I have for when cutting your panel (or even drilling) is to place a few layers of painters tape (masking tape) around the area you will be cutting. This helps protect the rest of the panel from slips. Also, it allows you to draw your dimensions right on the tape to help you when you cut. When you are done, you just peel the tape off. Also cut from the back side, not the side to be seen.
For rectangular cuts, drill holes along the inside of the rectangle edge. This will make it easier to cut. If the material is thin like crossroads posted, you can just use a razor knife to finish it. If it is thicker a side-cutting bit in a rotary tool might work.
I had the same issue of getting a finish I was happy with and eventually came up with something I was happy with.
I made an Instructable on making your own LCD window/bezel that ends up as a kind of black glass iPhone'esque type look. You could probably make the same kind of surround for a normal keypad if you could actually cut out the inside part, or use the same trick with a membrane keypad on the surface to have the black surround.
Cool. In the direction tack headed, one can make a piece of black paper and a window cutout, glue it to the back side of the clear acrylic. It’ll be easier to us that never knew what paint goes on what surface