Create or print a paper pattern for your gingerbread house pieces and have them ready.

Preheat your oven to 360 degrees F (180 degrees C).

Line a jelly roll pan with parchment paper and lightly grease it.

In a large bowl, beat the butter and brown sugar until light and fluffy.

Add the egg and molasses, and beat until combined.

Stir in the flour, ginger, baking soda, cinnamon, nutmeg, allspice, and salt until a thick dough forms.

Press the dough evenly into the prepared jelly roll pan.

Bake for 20-25 minutes, or until the gingerbread is a deep golden brown.

Let the gingerbread cool in the pan for 5 minutes.

While still warm, place your paper pattern on the gingerbread slab and carefully cut out the desired house shapes using a small paring knife.

Allow the gingerbread pieces to cool completely in the pan. Run your knife through the cuts again if needed.

Assemble the cooled gingerbread pieces using royal icing on a sturdy base, such as a cardboard cake board.

Decorate your gingerbread house with additional colored icing, Halloween candies, and marshmallow ghosts to create a spooky scene.