Working on a Shack with a Pyramid Roof

I am using bristol board for the sub-walls. THe building will measure a scale 12 foot square. Randum width boards will added to the subwalls. The walls will be nine foot tall. There will be two doors and six windows: front and back sides get a door and a window; the sides will host two windows per side. Four triangles will be cut from the bottom sheet. These triangles will measure thirteen foot across the bottom and will be six foot tall. Wall sections and material for roof sections.