Combine 1 part koji and 1 part water. Weigh this mixture and salt to 5 percent of the total weight.
Blend to increase the surface area of the inoculated starch. Transfer the ingredients to a non-reactive container, such as a glass mason jar.
Hold at ambient temperatures exposed to air. Mix the shio koji once or twice a day for up to 7 days. After 7 days your shio koji is ready. Store it in an airtight container in your fridge.