The night before you want to mix the dough, feed your sourdough starter so it is active and bubbly by morning.
If you are using dried blueberries, place them in a small bowl with orange juice. Cover and let them soak overnight. Strain before adding them to the dough.
In a large mixing bowl, add the active sourdough starter and warm water. Stir until the starter is mostly dissolved.
Add the sugar and stir again.
Add the bread flour, salt, and lemon zest. Mix until a shaggy dough forms.
Cover the bowl and let the dough rest for 30 minutes.
After the dough has rested, begin the stretch and folds. Take one side of the dough, stretch it up, and fold it back over itself. Turn the bowl and repeat on the other sides.
Do 3 sets of stretch and folds, waiting about 30 minutes between each set.
After the last stretch and fold, cover the bowl and let the dough bulk ferment at room temperature for 4 to 6 hours, or until it has doubled in size.
If using fresh blueberries, rinse and dry them well. If using frozen blueberries, keep them frozen until you are ready to add them. If using dried blueberries, make sure they are strained.
Lightly flour your work surface and turn the dough out of the bowl.
Gently stretch the dough into a rectangle. Do not stretch it too thin, or the blueberries may tear through the dough.
Place about half of the blueberries over the top half of the rectangle, leaving about a 1-inch border around the edges.
Fold the bottom half of the dough up over the blueberries.
Turn the dough so it is facing longways.
Place the remaining blueberries over the top section of the dough, again leaving a small border around the edges.
Fold the bottom portion of the dough up over the blueberries.
Gently shape the dough into a round or oval loaf, depending on the shape of your banneton. Try not to press too hard, especially if using fresh or frozen blueberries.
Place the shaped dough into a floured banneton basket. Cover and refrigerate overnight for at least 12 hours.
The next morning, turn the chilled dough out onto a piece of parchment paper.
Score the top of the dough with a bread lame or sharp knife. Keep the score shallow, about ¼ inch deep, so the blueberries do not push out too much while baking.
Place the dough into a Dutch oven.
Put the Dutch oven into a cold oven. Turn the oven to 425 degrees F and bake for 1 hour with the lid on.
After 1 hour, remove the lid. If the loaf is golden brown, remove it from the oven. If you want more color, bake uncovered for another 5 minutes.
Transfer the bread to a wire rack and let it cool for at least 1 hour before slicing.