When I saw this cardboard box house idea, I knew I had to make something similar.
I started out by cutting the flaps off the box and then gluing one of the longer flaps in the middle to separate the two floors. I planned on three rooms per floor. For some I glued down fabric as the carpet, and for the others I used different shades of acrylic paint.
Then I used the other flaps to make the walls that would get inserted in. I cut doors between them, and then Love Bug and I painted them.
Walls and floors painted, walls added in, and windows and doors cut. Love Bug also helped draw some of the shapes of the windows to cut out.
They loved it and immediately made it a home for Sesames, Minions, and Octonauts.