The icing does harden rather quickly, so you must work as fast as possible. However, I have found that if you use a pastry bag, it lasts longer before hardening. So, it's best to gather all the things you will need before you start.
I begin by covering a large, thick piece of cardboard with aluminum foil, to be used as the base. Next, I cut off the top of two large juice cartons to my desired height and hot glue each one to the base. Then you can start gluing the graham crackers to the juice cartons, making arches with them to form the rooftops. Don't worry about the gaps as you will be able to fill them all in with the icing.
Once you finish filling in all the gaps with Royal Icing, add the candies however you like. You will also be attaching the candies with the icing. However, if you run out of the icing you can always use the glue gun again.
Things You Will Need For The Gingerbread House Assembly:
hot glue gun
glue sticks
red and green licorice sticks
assorted Christmas candies
1 bag of red hots
1 pkg. of small candy canes
1 box of graham crackers
1 large bag of powdered sugar
2 large egg whites
1 pastry bag
Royal Icing Using
Egg Whites:
2 large egg whites
2 teaspoons fresh lemon juice