Insert an opening pick at the bottom end of your phone.

If you can't manage to insert the opening pick between the back cover and the frame, you can use a suction handle to create a small gap.

Start to slide the tip of the opening pick to the bottom left corner and cut the adhesive with it.

Leave the opening pick in the bottom left corner to prevent the adhesive from resealing. Insert a new opening pick and start to cut the adhesive on the left side of the phone.