Lightly shake to remove any air bubbles and allow the mixture to harden before removing from mold. Garden Molds X-CRD8006 Celtic Round Stepping Stone Mold- Pack of 2 Iron oxide pigments not included (sold separately). The Celtic Stepping Stone Mold is a fun and distinctive way to make your own stones with ease. You can add color to your stones by adding iron oxide pigments to the pre-poured concrete or by applying concrete paints to the dried mold.