In a large bowl, mix active starter and water together until milky and bubbly. Add flour and sprinkle salt on top. Mix until you have a shaggy, slightly tacky dough with no dry flour remaining.

Cover the bowl and let the dough rest for 30 minutes at room temperature (autolyse). This allows the flour to fully hydrate and gluten to start forming on its own.

Perform 4 sets of stretch and folds, spaced 30 minutes apart. With a wet hand, stretch one side of the dough upward, fold it over the top, rotate the bowl 90 degrees and repeat on all four sides.

After the final stretch and fold, cover and let the dough bulk ferment until it has risen 60-80% in volume. This takes 3-8 hours depending on kitchen temperature.

Turn the dough out onto a lightly floured surface and shape into a tight round boule by folding the sides in and dragging across the counter to build surface tension.

Place shaped dough seam-side up in a banneton or towel-lined bowl dusted with rice flour. Cover and refrigerate for 8-16 hours overnight for the best flavor and texture.

Preheat a Dutch oven inside a 450°F oven for at least 45 minutes. Turn dough onto parchment paper, score the top, and lower into the hot Dutch oven. Bake covered for 25 minutes, then uncovered for 20-25 minutes until deep golden brown.