Measure out 15 grams of the starter (up to 50 grams), and add double the grams of lukewarm water, stirring with your fingers to mix. Discard unused portion.
Add the same amount of bread flour as you did water and stir to mix.
Place in a large jar and set in a warm spot for 12-24 hours, before placing the lid on and putting in fridge.
Do weekly.
Notes
The instructor (Vanetine Kitamura) recommended using whole wheat bread flour for the starter, but feel free to use regularĀ breadĀ flour.