No need to take measurements to build a model for a 3D-printer or CNC machine. This cover was made by hand with Instamorph, a plastic that turns soft when heated and strong when cooled down to room temperature.
There are plenty of cool cell-phone cases out there on the market, but they are all produced by someone else. Tome to take things into you own hands and make one yourself.
You could try to build the case around you phone. It would fit perfectly and, depending on how you shape it, never fall off accidentally. I wanted a case that I could take on and off. And I didn't want to risk damaging my phone. I had never worked with Instamorph before.
My Idea was to make a copy of my phone and use it as a dummy to work on.
I already have a silicone case that I used as a mold to cast concrete in it. The concrete I used is meant to be used to build kitchen tops. To give it more strength it is mixed with fibers. So even though the block of concrete is just as thin as a phone, it is stable enough not to crack or break.
You could also try resins. Make sure to use some release agent then, otherwise your dummy might just get stuck in the mold. ;) The concrete came out perfectly without any release spray.
I just used some scotch-tape to seal the open holes and poured the concrete right in.
Tap it for a while so that the enclosed air-bubbles that are trapped in the concrete can float to the top and pop. Otherwise you will have tiny holes in your dummy.