I designed my minipcb2 board case for OnStep. The board project is here Minipcb2.
The case has 2 holes on the back side for various fasteners with a distance of 30 mm.
Print settings
Material: PETG
Layer Height: 0.2
Infill: 40%
Assembly
10pcs M3x5x5 threaded insert
8pcs M3x8 screw
4pcs M3x6 screw