Hmm, I'm not sure if you're mocking me or not
It's really simple – two larger tape strips that act as grip (I made sure they didn't cover the antenna strips). Try getting them as far out on the rounded edges as possible since this is where most of the grip is effective. As seen in the picture, I haven't been all that particular with this though. Then add a smaller strip that goes through the strap loop and is placed on the lower large strip. And finally another strip on top of it for extra security. I was a bit worried if the phone heating up might melt the tape glue, but that hasn't been an issue at all.
I really don't care about appearances (or second hand value) for my phone, but still I replaced the tape strips after about 6 months of uncaring use, since they get a bit "worn". Escecially around the rounded edges.
It's not pretty. But it is really functional. Even with not having the strap around my wrist, I still feel like it's a great extra security.