Modified and combined https://www.thingiverse.com/thing:2282201 and https://www.thingiverse.com/thing:1514531 to make a 37mm filter/lens mount for my iPhone 7 Plus, using Tinkercad. This is my first Tinkercad project.

Lightweight filters are held in with friction, but I would recommend gluing a UV filter or step ring in place if you are going to use heavier lenses or adapters. I use a 37mm to 58mm step-up ring with a 58mm fisheye lens, and while it does stay in, I can tell that over time it's going to pull out so I intend to glue a UV filter in place in the near future.