When the back panel is heated, apply the suction cup close to a corner of the phone. Lift up and insert a halberd spudger or opening pick under the rear glass.

Slide the blade of the Halberd spudger along the edge of the phone to separate the adhesive.

Follow around the edge of the phone, and use an opening pick or other tool (such as a plastic card) to keep already opened portions from re-adhering.