I remixed Zack Freedman's amazing Gridfinity Window Divider Bin - see his listing for Gridfinity details and which microscope slides to buy. I added a slot so that the microscope slide, well, slides in - no tape required! You can either leave it like that (very sturdy and usable for me) or also print the faceplate. You then slide that on top of the glass (also in rails) and apply a drop of superglue to either side, making the whole thing very sturdy with no tape.
I am new to 3d modeling so the STLs are a bit messy, but printed great for me. Please remix and improve if you can!
The tolerances are tight on this one, so please remix / comment if it seems too tight or loose for you!
**For the faceplate, I printed it upright with supports, so that the thin side bars would be fully vertical (see slicer image for what I mean - it's on the plate in the same orientation it ends up in in the model.) I didn't try any other orientation, might be fine.