A simple phone holder that fits on a microphone stand
First download the files from Thingiverse and 3D print the base. The STL file will be good for most microphone stands, but the OpenSCAD file is included if you need to tweak the settings for yours.
Laser cut the holder.
Use a [very] hot air gun, reflow, or heated wire to soften the holder's fingers and bend them round some wood. Remember to leave enough room for the phone, a phone case, the heads of the screws, and a little space to insert and remove the phone.