Mix the filtered water, pickle brine, and bread flour in a large bowl until a shaggy dough forms. Cover and let rest (autolyse) for 45-60 minutes.

Add the active sourdough starter and fine sea salt to the dough. Dimple and fold to thoroughly incorporate for 3-5 minutes. Cover and rest for 30 minutes.

Perform one set of stretch and folds. Cover and rest for 30 minutes.

Mist the counter lightly with water. Gently stretch the dough into a large thin rectangle (lamination). Scatter the dried, chopped dill pickles and fresh dill evenly over the dough. Fold into a neat package. Place back in bowl and rest 30 minutes.

Perform two additional sets of coil folds, spaced 30 minutes apart. Then let the dough bulk ferment undisturbed until increased by 50-75% in volume.

Turn the dough onto a floured surface. Pre-shape into a loose round and let rest for 20 minutes.

Final shape the dough into a tight batard or boule. Place seam-side up in a rice-floured proofing basket. Cover and cold retard in the refrigerator for 12 to 24 hours.

Preheat a Dutch oven in the oven at 500°F (260°C) for 1 hour.

Turn the dough onto parchment paper, score the top with a bread lame, and carefully transfer into the hot Dutch oven. Cover and bake for 20 minutes.

Remove the lid, reduce the oven temperature to 450°F (230°C), and bake for an additional 20-25 minutes until deeply browned.

Remove the bread from the Dutch oven and allow it to cool completely on a wire rack for at least 2 hours before slicing.