Flip over the cover, allowing the buttons to fall into your hand.

Be ready to catch all the buttons, some are very small. If a button does not fall out apply gentle pressure from behind.

When reassembling, put each plastic button in its allocated slot. Each button only fits snugly in one slot.

The best option for you is rotate the Wii Controller by 180°. If you obey this note, the small parts wont fall off and then you can remove the buttons.