Create a rough template of your stones by tracing the outline of the dinner plate on the back side of the cardboard. Leave three to four inches between each traced circle.
Cut a series of irregularly shaped pieces of cardboard using the size of the dinner plate as a guide. Do not cut around the exact outline of the plate. Each stone will be similar but will have a slightly different size and shape.
Paint each piece of cardboard with a base coat of gray paint. Set aside until fully dry.
Use the sponge to apply a second coat of darker or lighter gray paint over the entire base coat, to create a textured look. Dab the sponge lightly in the paint, then blot it on the base coat. The base coat should show through the sponge prints.
Lay the stones next to each other spaced two inches apart. Form a straight path for a more formal look or a relaxed, curvy path.
Secure the cardboard stones to the floor with a rolled piece of duct tape once the layout is finalized.