Before starting make sure it is off.

Remove the SD card.

Separate the back cover, unhooking it around the entire contour with an opening tool.

Peel the buttons off the frame with the metal spatula.

Finally, unglue the flex from the base plate. To do this, run the pins with the tip of the soldering iron while holding the flex with tweezers. After several passes with the soldering iron on the pins, the flex will come off without having to pull a lot.