How to make sourdough starter. 60g unbleached organic bread flour (I used King Arthur) 60g filtered water Mix ingredients in a jar. Loosely cover for 24 hours. Day 2: Stir once, then loosely cover until day 3. Day 3-7: Pour out half (60g) of the starter. Feed 60g flour and 60g of water. Mix, cover loosely and rest 24 hours. On day 7 up to 6 hours after your feeding refrigerate if active. By active, meaning it doubled in size and has bubbles on the surface.