Day 1: Mix 1 cup of whole wheat flour and 1 cup of water in a glass jar. Cover with a cloth and secure with a rubber band. Let it sit at room temperature.
Day 2-5: Each day, discard half of the starter and feed it with 1 cup of flour and 1 cup of water. Stir well, cover, and let it sit at room temperature.
By day 5, the starter should be bubbly and have a tangy smell. It's ready to use.