To make it you'll need:
chalkboard paint (optional)
Download the PDF for full instructions, but keep reading if you'd like to see detail shots of some of my construction techniques...
This is where I joined the two boxes together on the side of the house above the window (step 9). I overlapped the edges, ran a couple pieces of tape lengthwise on both the inside and outside, then wrapped tape around the seam to really hold it together.
The side walls seemed a little flimsy because they weren't a solid piece of cardboard, so I taped one of the flaps I removed from the top of the box (step 3) under the window to help strengthen the wall (step 10). Simple solution, but it seemed to make it much sturdier.
The flaps at the top and the bottom of the boxes were pre-cut, so I taped over the cuts to prevent weak spots on my roof and walls (step 4).
The flaps that I left attached to the box were folded down and taped to the sides to help support the structure (step 6). Once I added the roof they turned into convenient shelves to store light toys and books. To prevent the shelves from collapsing, I added a support made from cotton twine. I used an upholstery needle to poke through the ceiling and the bottom of the shelf and tied the ends together.
I didn't want the cardboard roof or the shelf to tear so I added a small piece of cardboard above the roof and below the shelf to prevent the twine from ripping through.
I figured the base of the door would eventually tear off (since it was thin and was bound to get stepped on a lot), so I covered it with duct tape which seems to be holding the doorway together quite nicely. I also ran duct tape around the edges of the door to keep those from getting torn up. The "welcome mat" is actually a larger piece of cardboard that runs under the floor of the house to help stabilize the entrance.
For the curtains, I sewed a channel at the top and ran a shoelace through it. I made two small slits in the cardboard above the window and simply ran the shoelace out one hole and in the other and tied the ends together.
For the chalkboard, I used two coats of chalkboard paint - let it dry completely between coats. The hooks are stick-on Command Hooks from 3M.
As with the shelf support, I didn't want the doorknob to get torn out so I cut two small pieces of cardboard and glued them to either side of the door. I used a bolt that was big enough to go through the glass knob and the 3 layers of cardboard, and used a knob of the back of the door that screwed onto the end of the bolt.
The flower box was made from a few small pieces of leftover cardboard. I attached it in basically the same way I did the curtains, but ran duct tape through the slits in the cardboard instead of a shoelace.