Cut four pieces of wood from 2-by-4-foot pieces or wider. Salvage old doors, windows or wood from a bookcase or dresser if you want an up-cycled bed.
Butt the pieces against one another in a rectangular shape. Nail or screw the pieces together.
Place the bed on the hill, digging out a bit of earth to wedge one side in slightly on a very steep hill.
Prop up the lower side with bricks or blocks to level the bed. Place a level in the center of the bed to make sure the bed sits evenly. Adjust bricks or blocks as necessary, digging them further into the ground, or adding earth beneath them to raise them.
Pound stakes into the inside corners of each side of the bed, if desired, to replace the bricks. Screw the stakes to the bed frame, and remove the bricks or blocks.
Cut a piece of lumber measuring the empty space beneath the bed. Wedge it into the space, and nail it to the frame to secure it.