Gently lever apart the lower and upper plastic covers of the keyboard, starting with the skinny edge (important!) and working towards the fat edge.

For tools, use something very skinny and strong, like a precision flathead screwdriver, then proceed with a larger flathead screwdriver.

Work gently to avoid snapping the locking parts of the plastic surrounds. The fat edge of the keyboard is held together more securely. Separate the covers at this edge last by gently wriggling that edge by hand until it releases.