Now that we have displaced the lower half we need to move to the front of the mouse.

There will be two crevices that are attaching the base to the shell of the mouse.

Using a spudger, gently and carefully pry along the dotted red line marked in the first photo until the shell and the base are separated.

As soon as the base and shell are separated, be careful not to pull them apart as they are still connected via a power and ribbon cable.