In a glass jar, combine 100 grams of whole wheat flour and 100 grams of room temperature water.
Stir well using a plastic or wooden spoon until there are no dry bits of flour.
Cover the jar loosely with a clean cloth or paper towel secured with a rubber band.
Leave the jar at room temperature for 24 hours.
After 24 hours, check for bubbles. Discard half of the mixture from your jar.
Add 50 grams of whole wheat flour and 50 grams of room temperature water to the remaining mixture.
Stir well and cover loosely again, allowing it to rest for another 24 hours.
On Day 3, discard half of the mixture again.
Add 100 grams of all-purpose flour and 100 grams of water to the remaining starter and mix thoroughly.
Cover loosely, and let it sit for 24 hours.
On Day 4, repeat the process: discard half of the mixture and feed it with 100 grams of all-purpose flour and 100 grams of water.
Mix, cover, and let it sit for another day.
On Day 5, your starter should now be bubbly. Discard half of the mixture once more.
Feed the starter with 100 grams of all-purpose flour and 100 grams of water, mix well, and let it sit for a few hours.