On 3 corners of the box lid I inset the top of metal tacks. Inside the box are 3 aligned magnets to (weakly) secure the lid. There is no good reason for this other than I wanted to do it.
The switch assembly is hot glued in place.
The “ones” digit is not hooked up to anything, it is simply a placeholder. The resistors (1%) are accurate enough for me (even though the picture clearly shows 18%…).