Ivan's mount is good and solid, but it's not well suited for phones with big camera bumps - for example, my Google Pixel 10 Pro has a 3.4mm camera bump and when clamped into the mount it gets severely slanted.

This is a simple sleeve that acts as a buffer to align the phone to the ocular. I recommend printing it in TPU because the model has 0 tolerances. If you want to go with hard plastics you'd need to adjust XY-hole compensation to make it fit the mount.

There are ready-made models available for different bump depth, but if you want to make it fit your phone perfectly - you can use the 5mm version (available in STEP format too) and cut away excess in the sliced or CAD.