Feed your starter and place in a warm place for 4 hours or until it has at least doubled.
Begin the autolyse process by mixing flour and filtered water. Cover with a damp towel and rest for 30 minutes.
Add your starter to the dough and mix in. Cover with a damp towel and rest for 30 minutes.
Add the salt to the dough, wet your hands with bottled water, and mix it in until combined. Cover with a damp towel rest for60 minutes.
Perform a series of folds to the dough to strengthen the gluten in the dough so that it will eventually hold shape. Cover with a damp towel rest for 60 minutes. Repeat this process 3 more times. After the last fold, cover and rest for 30 more minutes before pre-shaping.
Remove the dough and place it on your countertop. Shape into a boule. (Watch online tutorials for this and practice.) Transfer the dough seam side up into a lightly floured banneton (or bowl if you don’t have one)
Cover in plastic, a towel, or in a large plastic zip bag and refrigerate for 12-16 hours or up to 24 hours.
The next morning, preheat your Dutch oven in the oven at 250°C for 30 minutes.
Sprinkle semolina flour into the bottom of the Dutch oven.
Remove the dough from the banneton, place it on top of a parchment paper.