In a large bowl, whisk together bread flour, 1 cup oats, 1/2 cup seeds, salt, and yeast. Add water and mix until a shaggy, sticky dough forms with no dry flour spots. Cover bowl tightly.

Let the dough rise at room temperature for 12-18 hours, until bubbly and more than doubled in size.

Turn the dough out onto a heavily floured surface. Gently shape into a rough ball by folding edges toward the center.

Place the shaped dough, seam-side down, into a floured towel-lined bowl (or on parchment paper). Sprinkle with extra oats and seeds. Cover and let rise for 1.5-2 hours.

30 minutes before the end of the second rise, preheat oven to 450°F (230°C) with a Dutch oven and lid inside.

Carefully remove the hot Dutch oven. Transfer the dough into the pot (seam-side up is fine). Cover with the lid and bake for 30 minutes.

Remove the lid and continue baking for 15-20 minutes, until the loaf is deep golden brown and sounds hollow when tapped.

Cool the bread completely on a wire rack for at least 1-2 hours before slicing.