Mix ½ cup whole grain flour with ¼ cup lukewarm filtered water in a jar. Stir until smooth, cover loosely.
Place in a warm spot (70°F/21°C).
Let sit for 24 hours.
Discard half the starter. Add ½ cup all-purpose flour and ¼ cup filtered water to the remaining mixture. Mix well.
Cover and let sit for 24 hours.
Repeat the Day 3 feeding process.
Feed daily: discard half, add ½ cup flour and ¼ cup filtered water.
