Apply lever force on the upper part of the case behind the L button using an opening tool. Make sure to pry towards the back plate. Repeat the step with the R button.

After the hooks on the upper left and right side of the controller have come loose, the back panel can be lifted carefully to open up the remaining hooks on the bottom.

All in all, the back plate is connected to the front by eight hooks spread across the sides and the bottom of the plate.