Turn off the controller and remove the batteries
Remove the battery cover
Peel off the two rear grip stickers if present
Remove the hidden screws under the stickers
Remove the screw inside the battery compartment
Use a plastic pry tool to separate the front and back shells
Work around the edges to release the clips
Lift off the back shell carefully
Disconnect the internal ribbon cable if needed
Remove the remaining screws holding the internal parts
Lift out the motherboard and buttons carefully