The plumbing and such are all in the box side and the bedroom/living room folds out, then the far wall folds up and out. Then the two side walls fold out from inside.

All plumbing/cabinetry is in the pre-assembled, stationary spot. Maybe some recessed lighting in the foldable roof that slides out, or the walls, and it runs pre-fed through the joints.

It's actually ingenious, and the only part not shown is the center cabinet in the living room, and that's probably in the kitchen for shipping and placed in during install. Easy enough to set mounts and then real quick drop it in.

Source: www.boxabl.com/..