To pour a 4-inch slab that measures 1 square yard, use six 80-pound bags of concrete, and for a 6-inch slab, use eight 80-pound bags of concrete. One 80-pound bag of concrete covers 4 square feet at a thickness of 2 inches.
Before pouring the slab, use concrete forms made of 2x4 or 2x6 lumber, depending on the depth of the slab preferred. Excavate the slab area to a depth 3 inches deeper than the slab desired, place and tamper 3 inches of gravel to give the slab a base upon which to sit. After pouring and leveling the concrete, remember to let it cure.