Prepare the phone frame surface by removing all traces of adhesive.

Use tweezers to pull adhesive chunks off. Use the opening tool to scrape residue off. You can use high concentration (over 90%) isopropyl alcohol to help dissolve residue.

Be careful not to damage the wireless charging coil when scraping around it.

If you are re-using the rear cover, prepare the inner surface by removing all traces of adhesive from it.

Do not attempt to remove the rectangular plastic liner near the bottom of the cover, but do scrape off all adhesive on it.