For more designs visit: 

https://cults3d.com/en/users/UniqueDude/3d-models

https://www.thingiverse.com/shitshappen/designs

Note:

After printing you need to cut away accessible supports for hinge and carefully break open to release movement of hinges.

Update 05.06.2024.
Added updated version of phone holder, see link 

https://cults3d.com/en/3d-model/gadget/small-phone-holder-streamline