Use a Jimmy to pry between the midframe and back cover. Wiggle back and forward until the first clip releases.
Switch to a plastic spudger and continue gently prying along the edge of the back cover to release the clips.
Once all the clips are released around the edge of the cover, you will need to use a guitar pick to cut through adhesive on the top and bottom of the cover. Take care not to cut through the battery ribbon cable. The top adhesive is behind the glass feature on the back cover. You may need to apply some heat.