I am making a Tetris-style game, and for some reason when I place the blocks they are hanging just above the platform that I place them on. Is this the box collider or the character controller? I don’t know.
Though I would generally disagree with the use of a character controller in this situation (I don’t know the whys and wherefores of your project but a character controller seems way overkill for a tetris-style game), an easy, temporary fix might perhaps be to check the character controller’s height and radius. Maybe try to reduce its size to be a magnitude smaller than the collider to see how it behaves.
In any case, both the character controller and the collider prevent the object from going through the other, so one of them is probably redundant.