Method:

Preheat the oven to 180C prepare two baking sheets.
Whisk the flour, baking soda, ginger, cinnamon in a large bowl and set aside.
In a separate bowl using and electric whisk, cream the butter and sugar together until smooth and creamy. Beat in the egg, molasses and in tablespoon of water on high speed. Scraping down the sides as needed.
Fold in the dry ingredients. The dough will be very thick.
Roll the dough out between two pieces of parchment paper to about 5mm-8mm thickness.
Chill in the fridge for 2 hours.
Using a pizza cutter or small knife, carefully cut the dough into the gingerbread house template shaped. You will need two of each shape.
Gently transfer the dough shapes onto the baking sheet and straighten out the edges
Bake for 15-20 minutes our until lightly browned. Remove from oven and cool completely.

To assemble:
Use a wooden board as the base for the house. Place the royal icing in a squeeze bottle and run a thick line of royal icing on one long edge and one short edge of the side of the house piece. Stick it to your base an use any kitchen items to help it stand until set.
Run a line of royal icing along the bottom of the front of the house piece. Stick it to your base, adhering it to the side of the house piece. Hold the two in place for a few minutes until the icing is partially set, propping them up as necessary. Repeat with the 2nd side of the house piece and back of the house piece. Pipe royal icing inside any seams, inside and outside of the house, to fill any gaps.
Allow it to set for an hour before adding the roof pieces.
Run a thick line of royal icing on the inside edges of one of the roof pieces and attach it to the base. Hold in place for a few minutes. Repeat with 2nd roof piece. Run a thick line of royal icing where the two roof pieces meet at the top of the house and hold in place for a few minutes.
Use the left-over royal icing, buttercream and sweets to decorate the house as desired.