One of the easiest we've seen are these biscuit houses spotted over at El hada de papel. The structures are first constructed using cardboard which is then covered over in a layer of cookies or biscuits. Candies and other treats glued on over that using white icing is the final touch. They look good enough to eat and save lots on prep time. For other great craft ideas, check out El hada de papel.
(Image: El hada de papel)