Secure a suction cup to the back cover, as close to the heated edge as possible.

The suction cup will not make a good seal on the curved portion of the glass, so avoid putting it on the very edge.

If the phone's back cover is cracked, the suction cup may not stick. Try lifting it with strong tape, or superglue the suction cup in place and allow it to cure so you can proceed.

Lift the back cover's left edge with your suction cup, opening a slight gap between the back cover and the frame.

This may require a significant amount of force, but you only need to open a very slight gap with the suction cup to insert your tool.

If you have trouble, apply more heat to further soften the adhesive, and try again. The adhesive cools very fast, so you may need to heat it repeatedly.

If you're using an iOpener, follow instructions to avoid overheating it, or the gel pack may burst.