I use the avantree cellphone clip holder. Google that and it'll pop up.
It's basically a long arm deal that holds a cellphone. I clip it onto the table and point the phone down onto the test. Then you can see the test and my hands.
I'm up in the UP with minimal or nocell service from Thursday night until Tuesday night! I may be driving to a McDonald's 20 minutes away like 4 times a day to check my email! The anxiety is so real.
Unfortunately, LSAC does not provide cellphone lockers in any official capacity. But you should call your test center in advance and see if they can hold your phone for you. Some centers have done this in the past.