Use a plastic opening tool to separate the adhesive securing the back panel's left, right, and top edges.

Do not pry along the bottom (the edge opposite the battery compartment). There are a bunch of retaining clips that may break if you start from the bottom.

Be extremely careful in lifting off the lower panel. The primary CPU/chip on the circuit board (marked in red in the second photo) is affixed to the back panel with a blob of glue. Failure to carefully slice through the glue from the chip/panel can result in the chip being torn from the circuit board, which WILL destroy your trackpad.

After slicing through all the adhesive, the lower panel lifts right off.