This is what the finished house might look like:
Cut the wall panels out with a knife or handsaw; I prefer the straight square edges that the Japaneese style pull saw gives. Allow the edge of the roof to overhang the gable ends and the front/back walls an inch or so.
When you have the panels cut, paint them gingerbread brown. When dry, apply a bunch of white caulk to the joint surfaces and place them together, pinning them with a finishing nail or coarse threaded dry wall screw. You can see all the overflow of the joint can easily be caulked to make it appear the gingerbread is attached with flowing icing.
Children will look into the windows to see what's happening. I had little votive LED lights in the windows, and this year I put a small lighted tree inside along with a glass Santa ornament.
Any small garland or ribbon accent can be stuck into the wet caulk.
You can build a larger one out of 2" foam for a play house, or as I have done, a cool plant storage room that I keep heated to about 40*F. This one is 8' X 10'.
You could also build a larger gingerbread house as a lawn ornament and break it down for storage each year.