This does not permanently alter the Corsair 280X case. You can print both sides flat on the build plate if you'd like but there will be a texture difference. If you choose to use the full STL turn the model 45° in prusaslicer and bisect the model so you have a chamfered edge to glue instead of two squares. Also, there is a dovetail version if you're confident in your support profiles, removing supports can be pretty tight. When using the STLs in prusaslicer you'll need to split the STL into objects and lay them flat and make sure they're oriented in the correct direction(should just lay them flat on the same side and be fine). Printed at 0.010 Layer height for fine detail parts.
The author hasn't provided the model origin yet.