I bought and used the #00 screwdriver, and it worked perfectly for this.

I had also bought the #000, but I never needed it during the entire operation.

The 'flat head' holds it in place when down, and you can reattach your ribbon cable when it's up, it only needs to be partway in so when you close the flat head, if your joystick board can't move easily in place then you've done it right, it it's too loose, try again to work the ribbon cable under.

Make sure that you have removed your SD card, otherwise that'll keep you from completing this step.

I found that the rubber bumps don't move easily, you'll likely have to use a lot of upward force to move them.