1. Mix 50 grams of flour with 50 grams of water.
2. Put the mixture in a warm place (ideally 30 degrees Celsius or 86 degrees Fahrenheit).
3. When it starts to bubble (8 to 12 hours later), feed with 50 grams of flour and 50 grams of water. Stir well. Put back in the warm place.
4. When it bubbles again, repeat step 3. Keep repeating step 3 until you have starter. The quantity of the mixture will grow. If it's getting too big for your bowl, discard half before feeding.
Keep an eye on the mixture. Feed it when it bubbles. If you can't be there for long periods of time, move it to a cooler place to slow down the fermentation until you can watch it again.