A MagSafe-compatible mount (non-charging, just a holder) for iPhone 12 and later, with a 1/4"-20 thread on one side for a photographic tripod or similar. Requires 19 6x3 mm disc magnets - I used these. Make sure you get the orientation correct as you put them in - similar poles should face the center.

Print in flexible TPU for a non-marring mount, but PETG or PLA work fine too. Use a tool or hex key to push the magnets in. Works through cases that support MagSafe charging. Modeled in OpenSCAD; you could probably subtract a volume out of the middle on the phone side to accept the guts of a Qi charger and have a mount that charges, too.