You in a big envelope and collected a lot of paper squares, triangles and circles of various sizes and colors. Add to them the rectangles of different shapes - you'll have a "warehouse "building materials". Now you can start building houses.
Be creative with your child. From your "parts" you can build a simple house with a pipe, and a Palace. On paper, you can rebuild a house, moving the pieces until you get bored. When the little architect and Builder will get something interesting, stick his creation on paper.