1. Print out and your gingerbread house template
2. Preheat oven to 350º
3. In a mixing bowl, combine flour, salt, baking powder, and spices together, and set aside
4. In a larger mixing bowl, or stand mixer, cream butter and brown sugar together until fluffy
5. Beat in molasses, egg, and vanilla
6. Stir in dry ingredients. I find it best to add them about 1/3 at a time rather than dumping the whole thing in at once. 
7. Mix until dough forms a nice ball
8. Turn dough onto a floured surface, and roll to about 1/3 inch thick
9. Arrange gingerbread house template over dough, and cut with a knife or pizza cutter
10. Transfer dough onto a baking sheet, with an inch or so between each piece. the dough shouldn’t spread or rise, but you do want some air flow between pieces for even baking. 
11. Be sure to follow instructions on template for cutting two of each piece, etc. There is an optional chimney. 
12. If needed, gather dough scraps up and roll again to finish cutting. 
13. Bake pieces in oven for 15 minutes, until edges are fully set, and beginning to darken. The center should be slightly soft, but much firmer than you would want for a normal cookie. 
14. Remove from oven, and let cool completely on a wire rack. 

To assemble your house: 

1. Pipe a layer of royal icing onto side edges of house, and press gabled front and back sides to them, holding for about a minute, until icing is set. 
2. Pipe another layer of icing over gables, and press roof pieces onto them, holding for another 1-2 minutes, until icing sets. 
3. Pipe a layer of icing along roof ridge to help secure roof. 
4. Decorate as desired.