once you've done the disassembly guide, remove these 2 screws.(thin screws) With a little twist, you can removed the joystick handle from the base. The roll pot just slides off once you've detached the stick.

Metal pin(in yellow) goes through the slot. you have to align the floating part below the shaft, twisted a little bit, and hold the spring down at the same time. This is probably the hardest part of the reassembly. you can practice without the roll pot installed, but roll pot must be installed for final assembly.