I don't particularly like the openflexure approach. Instead, I build stages similar to standard XY stages: https://www.asiimaging.com/products/stages/xy-inverted-stage... which uses standard motion components (linear rail and linear bearings, 3d printer style steppers), all of which gets mounted on aluminum extrusion (4040). Then the illuminator and camera just get mounted on the aluminum extrusion.

It's pretty close to the Thorlabs Cerna, https://www.thorlabs.com/cerna-r-series-modular-microscopy-s... although I just do low-magnification light microscopy.