Begin by gathering all your ingredients. Measure out 2 cups of whole wheat flour, 2 cups of all-purpose flour, 2 teaspoons of salt, 1 teaspoon of active dry yeast, 2 cups of water, 1 cup of sunflower seeds, and ½ cup of flax seeds.
In a small bowl, combine 2 cups of warm water (not hot) with 1 teaspoon of active dry yeast. Let it sit for about 5-10 minutes, until it becomes frothy.
In a large mixing bowl, whisk together the whole wheat flour, all-purpose flour, and salt.
Once the yeast is frothy, pour it into the bowl of dry ingredients. Using a rubber spatula, mix until a shaggy dough forms.
Fold in the sunflower seeds and flax seeds.
On a lightly floured surface, turn the dough out and knead for about 8-10 minutes, until it becomes smooth and elastic.
Place the kneaded dough in a lightly greased bowl, cover it with a kitchen towel, and let it rise in a warm place for about 1 to 2 hours, or until doubled in size.
Once the dough has risen, punch it down to release the air. Shape it into a round or oval loaf.
Place the shaped dough into your cast iron skillet. Cover it again with the kitchen towel and let it rise for another 30-60 minutes.
While the dough is rising, preheat your oven to 450°F (230°C).
Once the oven is hot and the dough has risen, place the cast iron skillet in the oven. Bake for 30-35 minutes, or until the bread is golden brown.
Remove the skillet from the oven and let the bread cool in the skillet for 10 minutes before transferring it to a wire rack. Allow it to cool completely before slicing.