Place the controller on a work surface with the joysticks facing down.

Use a spudger or your finger to slide the Release tab to the left. The front trim should fall to the table.

If the front trim doesn't fall open, make sure the front trim has room to fall down and the Release tab is pushed all the way to the left.

Lift the controller up, leaving the front trim on the table.

During reassembly, insert the front trim at an angle so the top slots in first, then lower the trim into place and snap it onto the controller.