The weak point of flat printed covers of this kind is the hook. It's prone to break - layers can separate under stress.
In this design the trapdoor can still be printed flat and the hook can be stress resistant at the same time. The hook is printed separately in a way that allows to glue it into a slot in the trapdoor. Use superglue or whatever that is strong and works for you. Let the glue dry for as long as necessary before installing in your Amiga.