Minecraft wiki entry for Building_micro_shelters, associated text: 8. While standing on the bed place the door on the same side of the bed that the crafting table and furnace is on.
9. Build a 2x2 wall around the structure with the solid blocks, do not place any blocks at the corners to conserve resources.
10. Make a roof using all 12 of the (cobble)stone slabs, be sure to cover both the door and all the walls.