Cover your work surface with newspaper or plastic sheeting.
Use petroleum jelly to generously coat a stepping stone mold. An 2-inch deep aluminum cake pan can be used as a mold.
Prepare the concrete by following the manufacturer's directions on the bag of concrete mix.
Pour the prepared concrete into the mold 3/4 full. Smooth it flat with a large spoon and tap the outside edges of the mold to help release any air bubbles. Allow the cement time to set up--45 to 60 minutes--before embellishing or making hand/foot prints.
Decorate your stepping stone with shells, beads, or marbles, or make a hand/foot print by firmly pressing a hand or foot into the cement. Set decorative items deep enough to prevent them from dislodging. If you make a mistake, smooth out the cement, tap the sides and decorate again.
Let your stepping stone sit for 3 days without being disturbed. Carefully remove it from the mold by turning it upside down and catching it in your lap or hand. Wait about 1 week before placing your stepping stone outside.