In re-reading the tutorial, I realized I forgot about the step where you grout the stones. It does make it look more like a real stone house, so I'll probably go back and do that part, it would make it sturdier as well. I didn't use liquid nails, I used some adhesive from Joann's that said it was weatherproof. I used a different sort of moss for the roof and oh, forgot to spray seal that. Read the tutorial at Duckyknits, don't use any instructions I'm giving here!
Mine was also a lot easier to make because I found a birdhouse at Joann's that had a regular door opening instead of a round hole. The plastic door frame was part of the original birdhouse, I didn't need to add that. I had just painted it and put it in the garden last summer, both girls agree it looks much better with the stones and moss added.