Who says cassettes have no purpose these days? As it turns out, a case for a Mini-DV tape is the perfect size to act as a smartphone stand.
You've probably got one of these laying around, just use the case for your brother-in-law's cousins graduation or whatever tape you're never going to look at again, turn it inside out and you're good to go. An audio cassette case works too if that's all you have.
It's sturdy. It's the perfect angle. It's cheap.