In a large mixing bowl, whisk together 2 cups baking soda and 1 cup cornstarch until evenly combined.

Slowly add 1 1/4 cups water, stirring continuously until you reach a thick paste — like damp sand. Add a little more water if it seems too dry.

If using color, divide the mixture into portions and add a drop or two of food coloring or natural pigment to each. Mix until color is uniform. (Tip: use gloves to avoid staining hands.)

Decide when to add essential oils: Method A (strong scent now): Add 10–15 drops essential oil per batch and stir thoroughly. Method B (best scent retention): Form and dry the stones first, then add oil drops after drying (recommended for baking/oven drying).

Press the mixture firmly into silicone molds or shape stones by hand. Tap the mold gently to remove air bubbles and smooth the tops. Add dried flowers or a sprinkle of activated charcoal for contrast while mixture is wet.

Drying options: Air-dry: Place stones on wax paper or a rack and let them dry 24–48 hours, flipping once so both sides cure evenly. Oven method (faster): Preheat oven to 200°F (90–95°C). Place stones on a baking sheet lined with parchment and bake 60–120 minutes, flipping halfway.

Once completely dry and hard, remove gently from molds. If you didn’t add oils before drying, use a dropper to add 2–4 drops of essential oil to each stone now. Allow oils to absorb 1–2 hours before placing them around the house.

Enjoy! Place stones in small bowls, sachets, drawers, cars, or gift boxes. Refresh scent with a few drops of oil every 2–6 weeks.