When you say "bottom plate," do you mean the base of the carrying case? If that is what you meant, and you are still wondering how to remove the typewriter from the base of the case, there are two screws that secure it to the bottom. They are accessible through the keyboard. You can see them if you look underneath the back corners of the keyboard--near figure key and the color selector.

If you are wondering what the base looks like underneath, without the typewriter, it is pictured below. You can see where the back feet fit toward the rear edge. The bolts that secure the typewriter (pictured out) fit through a rubber spacer/foot and screw into the base, near the middle of the case bottom. The front feet of the machine rest just in front of the rubber spacer, where you see a little worn marks.