Very simple: there is a slot through the bottom plate that is hidden under the product label. Take the label off, and the slot will be visible. This is a window that gives you access to the screw at the bottom of the engine shaft. Put a flat screwdriver head in the window and rotate the blades until the screwdriver sits in the slot of the shaft screw. Now keep the shaft steady and rotate the blade to unscrew. No need to take the bottom plate apart. It is a pain in the neck, and you will almost certainly break the latches that hold the bottom plate in place.