Alternatively, you can stack small objects around the back to level out the height of the cameras.

Lay strips of tape around the perimeter of your device to protect it from scratches.

Stack coins or similar objects around the perimeter so they're roughly equal to the height of the protrusions in the back cover.

Place heavy objects, such as multiple books, on top of the coins and leave them for a few hours. Don't use any valuable books, as the coins might leave an impression.