Pour 1.5 cups of warm water into a large bowl, then add 1 cup of active sourdough starter and 3 cups of flour. Stir it all together just enough to get the flour mixed in, but don't knead, and don't worry about little lumps and inconsistencies. Cover the bowl with a tea towel and let it rest at room temperature for 30 minutes.

After 30 minutes, add 1 tablespoon of salt to the dough, get your hands wet, and use your hands to work the salt into the dough for a minute or so. Then cover the dough with a towel.

Stretch and fold the dough. Cover the bowl with a towel, and let it rest for 30 minutes. Repeat the stretch and fold process followed by a 30-minute rest 3 times.

After the third stretch and fold, cover the dough and let it rest until it is doubled in size, which could take anywhere from 2 to 12 hours.

Add 1 tablespoon of flour, 1 cup of frozen blueberries, and zest from a whole lemon to a small bowl and stir gently to coat the blueberries in flour. Set aside.

Once the dough has doubled in size, turn it out onto a lightly floured work surface and stretch it into a big rectangle. Spread ⅔ of the blueberry lemon zest mixture over the dough rectangle.

Fold one of the long sides of the dough over to bring the edge to the middle of the rectangle, then fold the other long side over the top of the first side. Spread the remaining ⅓ of the blueberry-lemon zest mixture over the dough.

Roll the dough up into a ball and place it seam side down in a banneton basket. Cover and cold-proof for at least 2 hours, up to 24 hours.

Preheat a dutch oven at 425F for 30 minutes. Remove the dough from the fridge, turn it out onto parchment paper, and score the dough.

Place the dough in the hot dutch oven and cover it with the lid. Bake at 425F with the lid on for 30 minutes, then remove the lid and bake for another 8-10 minutes until golden brown.

Let the loaf cool for at least an hour before slicing.