For some reason the knife is the only way to get the correct angle and pressure to make the rubber feet release. Use of other tools is not recommended.

There are four rubber feet covering the four casing screws. Carefully using a sharp knife, these may be lifted out.

Use a Philips screwdriver to remove the four screws and set them aside.

These sticky rubber feet are best gently stuck next to the corresponding exposed screw hole, to minimize risk of loss. They will not leave a mark.