It's possible in principle to prepare your "flat" PCB for installation in a box, but it is not for the faint-of-heart... I had a section on this in the earlier edition of the user manual, but have removed it in the more recent version because the risk of damaging the PCB seemed too high -- especially with all the components already installed:
The dividing line between the plugboard and the main PCB is not pre-scored, since there are traces connecting the two on the bottom side. So you can't simply break off the plugboard, but either need dedicated PCB shears which can clamp the PCB without any slippage. (But clamp it only on one side, since there are components on the mainboard side
quite close to the cut.) Or you need to score the PCB with a knife many (!) times and then bend and break it -- supporting the populated main board to avoid bending stress in that part, but without crushing the components in that area.
You will also need to unsolder the USB plug from the plugboard, and find a pigtailed USB jack to mount into the case instead. (There are solder pads for this on the main board.) The audio surface transducer will need to be replaced by a case-mounted speaker since the separated PCBs don't offer a suitable mounting area. Finally, solder SMD pin headers to the main board and plugboard and connect them with a ribbon cable; that step is relatively straightforward.
If this does not scare you, I can dig up the old text from the user manual which has a little more detail. CEDS would have to comment on the possibility of making the case available on its own. My gut feel is that shipping costs would be rather high in relation to the box price, so this may not be an attractive option?
Best regards,
Jürgen