Break Up the Koji: Place your rice koji into a clean bowl or directly into your storage container. Using your hands, gently rub the koji together to break up any large clumps. You want every single grain to be free and separated so it can absorb the water evenly.
Combine and Mix: Add the salt and water to the container with the separated koji. Stir everything thoroughly using a clean spoon or silicone spatula. Ensure the salt is fully distributed and the koji grains are completely submerged in the liquid.
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Notes
Pro-tip: If you are using shop-bought dried koji, you will need to add extra water as the koji absorbs moisture. (If using fluffy dried koji, the amount of water required may almost double.) Make sure to maintain a salt concentration of 12%.