I designed this to fit my iPhone 12 Pro. I don't know if the dimensions for the 12 Pro and iPhone 12's are the same, so I don't know if it will fit a regular 12 or 12 Pro Max. If you try on something other than a 12 Pro, please leave a comment to let me know how it worked.

There are three different versions to choose from.

Dimensions (from digital calipers) of my 12 Pro I used when designing to help you decide if it fits another iPhone:
Length=146.8 mm
Width= 71.6 mm
Depth=7.9 mm

Camera Hole= 33.6 mmx 31.1 mm

If you want the symbols to be a different color, then change at 13 mm.

By the way, the point on the end of the X is pretty sharp. I couldn't angle it so it wasn't so sharp in the design, so I just use my nippers and cut it off at 30 degrees or so. Now it doesn't catch on my pocket or fingers.

I upgraded my Ender 3 Pro with a direct drive extruder so I could print TPU. However, I did try printing this with PLA, and it seems to work. One corner did pull up from the bed, so it didn't fit perfectly, but I think it might still work. If you try PLA, please leave a comment to let me know how it worked.

Creality

Ender 3 Pro

No

Yes

.2 mm

10%

I used about 7% triangle support touching build plate. The grid or lines pattern also works well at 7%. Also, make sure the overhang angle is like 85%. I printed one and didn't check that. It was set lower, like 65% and it supported the bevel on the front edge that left several bumps that I've never been able to completely get rid of.

If you are using TPU, DO NOT use support interface (where the infill gets more dense as it approaches the overhang). That makes removing the support very difficult.

I used a brim because there is not a lot of surface area of the edge that touches the build plate.