Based on a model on another site, I made it simpler for my printing. My version is slightly wider but has the telescoping arm for fine-tuning the angle. I printed with 0.8mm nozzle and 0.4mm layer height.

I used 3 M3x10 screws but M4 should work if the holes come out oversized in your prints.

I would print the telescoping arm separately so that you can adjust scales depending on how it slides.

The fixed arm has a hole for a locking screw but mine doesn't need it.

I think the assembly is simple but let me know if you need any help.