You can set* the desired space from the wall and some other parameters. Note that the box dimensions are a bit larger than needed, becuase it is easier to fill a larger box with some paper than to somehow enlarge a small box.

I use it a bit differently than originally designed, but it's good enough, I think.

*) Open in Customizer and set the value. You can use either Thingiverse customizer (Thingiverse account is needed) or OpenSCAD Customizer (OpenSCAD in your computer is needed).

Prusa

I3 MK3S

Doesn't Matter

No

0.1mm

The first print attempt was screwed, so I disabled retractions and tried again.