Minecraft wiki entry for Survival_in_an_infinite_desert, associated text: First a 5×5 (exterior) sand block house, 3 blocks high (solid roof at the 3rd level). Cactus for a door. Then, a 2-deep ditch at least 3 clear blocks distant from the walls. Then, a zigzag cactus ring and then an outer ditch. Or you can make a simple portable shelter with: