Patterns: We don't use patterns with pieces larger than 8 1/2 x 11 (especially roofs) because the gingerbread doesn't seem strong enough. We shrink or enlarge patterns on xerox machine as desired, including to get a smaller version of a larger house (sometimes enlarging windows a little or eliminating fussy details).
Decorating: Attach all decorations to pieces and allow them to dry before assembly. Nothing too heavy on roofs; nothing to far out on walls. Adults and older kids use a pastry tube with icing to attach decorations; for very young kids, we ice a whole piece with the icing and the kid places decorations as desired.
Assembly: Using a thick line of royal icing (through pastry tube with tip with large opening), first attach one side to the base. The attach two perpendicular sides to each each other and to base. Then attach the other two sides, one at a time to base and adjacent side. Support with tin cans as it dries. Let dry at least one hour. Attach roof pieces with icing. Let dry at least one hour, supporting with tin cans as necessary.
Stained glass windows: Heat a hard candy (or several crushed hard candies) on aluminum foil in a 350 degree oven for 5 minutes. They may get a little bubbly, which is fine. Peel off when cool.
Foil base: Mount house on cardboard and decorate all the cardboard with icing snow. Let dry. Cut a piece of cardboard 1 1/2 inch bigger on each side than the base; cover with green or red foil. Mount the case cardboard with the house on the foil, glueing with icing. Put candies around the edge of the base to hide the cardboard edge and give the effect of a fence. Make base at least 3 inches larger on all sides (4 in front) than the base of the house to allow for landscaping on small houses (more for medium or large houses). Situate the house toward the back and one side to allow for a sizable yard to decorate.
Trees: Sugar ice cream cones covered with green royal icing.
Ice/Snow effect: Sprinkle crushed blue mint candy on trees and snow. Powerdered sugar can also be used.