Mix ½ cup whole grain flour with ¼ cup lukewarm filtered water in a jar. Stir until smooth and cover loosely.
Place in a warm spot (around 70°F/21°C).
Let it sit for 24 hours.
Discard half of the starter.
Add ½ cup all-purpose flour and ¼ cup filtered water to the remaining mixture. Stir well, cover, and let sit for another 24 hours.
Repeat the feeding process from Day 3.
Continue feeding daily by discarding half, and then adding ½ cup flour and ¼ cup filtered water.
