With just water and flour, you can make your own sourdough starter for all your homemade bread recipes!
Start the process by adding 1⁄2 cup whole wheat flour and 1⁄4 cup water to the jar. (If you need more flour to reach a pancake batter consistency, you can add up to 1/4 cup more.)
Stir thoroughly and cover with a towel and rubber band. Let sit for 24 hours at room temperature. (Try to keep it in an area of your house that is somewhat warm. Very cool rooms tend to slow the action of a starter.)
After 24 hours, check the mixture for bubbles. If you see some, add 1⁄2 cup all-purpose flour and 1⁄4-1/3 cup water. If you don’t see bubbles, give it a stir and let sit 24 more hours.
Check for bubbles again. If you do see bubbles, remove half of the starter, add 1⁄2 cup all-purpose flour and 1⁄4-1/3 cup water and stir thoroughly. Let sit 24 hours.
Remove half of the starter, and feed with 1⁄2 cup all-purpose flour and 1⁄4 cup water, stirring thoroughly. Let sit 24 hours.