Prepare the Potatoes:
If using fresh potatoes, boil and mash them until smooth. Let them cool before adding to the dough. For potato flakes, rehydrate with warm water until creamy.

Mix the Dough:
In a large bowl, combine the sourdough starter, mashed potatoes, bread flour, water, and salt. Mix until a shaggy dough forms.

Knead the Dough:
Knead the dough by hand for 8–10 minutes or in a stand mixer for 5 minutes, until it becomes smooth and elastic.

First Rise:
Place the dough in a lightly oiled bowl, cover with a damp cloth, and let it rise for 4–6 hours at room temperature, or until doubled in size.

Shape the Dough:
Turn the dough onto a floured surface and shape it into a round or oval loaf. Place it into a floured proofing basket or bowl.

Second Rise:
Cover the dough and let it proof for another 1–2 hours.

Bake the Bread:
Preheat your oven to 475°F (245°C) with a Dutch oven inside. Transfer the dough into the preheated Dutch oven, score the top, and bake with the lid on for 20 minutes. Remove the lid and bake for another 20–25 minutes, until the crust is golden brown.

Cool and Serve:
Let the bread cool completely on a wire rack before slicing.