Flip the phone open with the back side still facing you.

Grasping the phone from underneath, use your fingers to push up on the keypad until the motherboard can be easily lifted up from the plastic outer casing of the phone.

When you do this the plastic camera button will pop out. It is not directly attached to anything. Make sure to save it for reassembly because it must be placed back on its tab at the side with the camera icon facing right side up to work correctly.