Day 1: Begin by combining 100 grams of unbleached all-purpose flour with 100 grams of filtered water in a glass jar. Stir the mixture thoroughly to form a thick, pancake-batter-like consistency. Since we are just mixing flour and water together, there should not be much of a smell at this point. Cover the container loosely with a lid or cloth to allow airflow. Do not cover the jar tightly. Let it sit on the counter for 24 hours.
Day 2: Time for it's first feeding! Discard half of the mixture and keep 100 grams of your sourdough starter to a glass jar. Add 100 grams of filtered water and 100 grams of unbleached flour. Mix well until a thick consistency forms. Covering loosely.
Days 3-5: Every 24 hours, repeat the process in Day 2. Each day, there should be more sourdough starter in the jar. Discard all but 100 grams of the starter and mix back 100 grams of water and 100 grams of unbleached flour. After each day, look for bubbles forming on the surface after feedings. This indicates the production of carbon dioxide by yeast activity. The starter should show signs of rising or expanding in volume after each feeding. There should also be a slight tangy smell in the starter after each feeding.
By day 6, you should see bubbles forming on the top of your starter, indicating the presence of active fermentation. It will also rise and almost double in size. If you smell your starter, you'll smell slightly tangy aroma and that is perfect! If you notice these signs, congratulations – your sourdough starter is alive and thriving!
Once your starter is established, maintain it by keeping it at room temperature and continuing with regular feedings. If you plan to bake frequently, you can store it on the kitchen counter. Otherwise, refrigerate in a closed glass jar and bring it to room temperature before each use.