I ordered some laser cut 2mm plexi with the holes on the corners (no holes for the components yet as I'm not sure about the alignment yet). Using some screws instead of spacers and drilling some more holes by hand gives rough picture of how this is going to look like when finished:

I'm happy about how it looks. The whole thing is 13cm x 13 cm x 3cm but as can be seen it may probably be reduced a little. We'll see when PCB is done.