Mix together all ingredients.

Cover or place in a glass jar with a tight-fitting lid and allow to ferment at room temperature for 24 hours.

Store in the refrigerator after fermentation.

Use as directed.

To replenish, add equal amounts of flour and water to replace what you've used. For example: if your recipe calls for 8 oz of starter, combine 4 oz of water and 4 oz of rye flour in a small bowl and pour back into the original starter jar to incorporate it into the remaining fermented starter.