use silicone baking pan, or a new ziplock (1/2 gal). Fill it with boiling water, then place it on top of the screen for 90 sec. Then remove it and place small suction cap near the top of the screen. Apply steady pull to the cap while holding the frame with other hand.

I used 1-gallon Ziploc back and poured 1qt of boiling water into it. I placed my iPhone on a corkboard and the bag on top for 120 sec.

It worked like magic. I just pooled the screen with the suction cup, and it got loose from the case. No heat damage. Everything works.