Need help removing the back cover

Need help removing the back cover

My camera lens is shattered. I ordered the replacement lens and adhesive from ifixit, and i also ordered a suction cup tool to pry it open. At first I was using a hair dryer for heat. It wasn't working. I then tried putting my phone on a pan on the oven set to the lowest setting. The back cover still won't budge at all. What am I doing wrong? Do I simply need more heat? Anything else I can be doing? How hot is it supposed to get??