It depends on the climate where you live. If it gets very cold, you'll want to start with a layer of brick around the inside edge to provide insulation. Then plywood exterior, with cloth interior for warmth and comfort. Because do houses are small structures, you won't need much of a frame work, just some connecting trusses for the ceiling.
If you are living in a warmer climate, forget the bricks and use triangular wood wedges to keep your base stable, make sure to provide a good amount of ventilation, too.