Unscrew the 2 M2.0 × 3.5 mm screws. Don't mind that I've already taken them amount (whoops, forgot to take a pic before).

Unstick the cable from the metal frame.

The cable connecting the IO board to the motherboard has some kind of glue connecting a part of it to the metal frame. To remove it, hold the cable (not the IO board) and pull with just enough force to slowly unstick it. Do it carefully.

If you want to, you can unplug the ZIF connector connecting the motherboard to the IO board, but it is absolutely not necessary for our purposes.