I browsed around the internet and like this design https://www.thingiverse.com/thing:25098 and just made some small changes.
For reference, my phone is an iPhone 11 in a Speck Presidio 2 GRIP case. I would assume the mount would work other phones in other cases since the arms have a fair amount of flex in them.
The only non printed part is the nut, which is pressed into place after printing.
Hope you find it useful and please rate/post your make.
I printed this using PETG, but other filaments could be used. Three perimeters and 4 solid layers top and bottom.
The author hasn't provided the model origin yet.