Step 1: In your clean glass jar, combine 60g (1/2 cup) unbleached all-purpose or bread flour with 60g (1/4 cup) filtered water. Mix thoroughly with a spatula until no dry clumps of flour remain. The mixture will be thick and paste-like.
Step 2: Scrape down the sides of the jar, cover loosely (to allow air circulation but prevent drying), and let it sit at room temperature (ideally 70-75°F / 21-24°C) for 24 hours.
Step 3: On day 2, discard half of your starter (about 60g), leaving 60g in the jar.
Step 4: Add 60g fresh flour and 60g fresh filtered water to the remaining starter. Mix well, cover loosely, and return to room temperature for another 24 hours.
Step 5: On day 3, discard all but 60g of your starter. Feed with 60g flour and 60g water. Mix, cover loosely, and let it sit at room temperature for 12-24 hours.
Step 6: On Day 4 & 5, feed twice a day, approximately every 12 hours. Each feeding: discard all but 60g, then feed with 60g flour and 60g water. Continue to mix, cover loosely, and leave at room temperature.
Step 7: On Day 6 & 7, your starter should be consistently doubling or tripling in size within 4-6 hours of feeding, showing lots of bubbles. When you feed it, it should feel light and airy. Perform the “float test”: Take a small spoonful of starter and drop it into a glass of water. If it floats, it’s ready to bake!