I often need to take hands free photos at work and I found the perfect thing lying around - a disused Bilora Tripod! Sadly it was missing the camera mounting plate that would allow me to attach things.
No problems though, as designing and printing a smart phone adapter was super straightforward.
It’s not necessary to join the two knob-halves as once they are threaded into the upper gripper their relative positions are constrained.
Overall the mount does a good job at holding the phone in place but it can still slide sideways with a bit of external force. Without redesigning the whole mount, a knurled inner surface or the addition of a foam or rubber layer would prevent sliding.