You speak or write or merely think these things and it is so: there is a box. A box supposes a room, that is, is supposes a place for a box to be and so there is a room around you, of infinite height and width and depth, of space infinite but nevertheless a room with a floor for the box to sit upon. In the beginning was the floor and your spirit moving restlessly upon its surface.
You think about rooms and that means walls for you so suddenly there are walls infinitely close and infinitely distant, indeed at no set distance, but walls, yes, of no particular color or shape but there they are, connected to the floor, and (by the very nature of walls) implying an outside, an other place beyond the walls. You think (or speak or write) a door and there is a door.
You make further assumptions and everything scales down to human sized. The door is just over six feet tall, the room is maybe twelve feet by ten and the box is, well, let us not worry about the box. Smaller than the room, obviously.
You go through the door and think the world and the world grows up around you, waiting only for you to LOOK AT it (or think it or say it or write it) for it to be, more than a collection of objects but then nothing more than that, anyway. A collection of nouns you verb yourself upon, and break without changing.