Add 8 inches to the length and width of the stove's floor space. Cut two boards for the length plus 8 inches and two for the width plus 8 inches. For instance, if your stove takes up 20 by 24 inches of floor space, cut two boards 28 inches long and two boards 32 inches long.
Nail the boards together in a box shape to create a 6-inch deep mold for the cement.
Place the mold on a flat part of the ground where you want to have your cast iron stove.
Fill the mold with prepared cement mix and let it dry overnight or as directed by the package instructions.
Remove the nails holding together the mold to take the boards off.
Place the cast iron stove on top of the hearth pad. The weight of the cast iron stove should keep it in place on the hearth pad.