Pour the water in the mixer bowl. Using a wooden spoon, stir in the yeast, flours, olive oil, coriander, and sea salt, just until it comes together as a dough.
Attach the dough hook and mix the dough on medium speed until it's supple, smooth, and elastic about 8 or 9 minutes. (My old 350 watt KitchenAid worked well at 3, though the recipe recommends 4. The KA was dancing across the counter at 4.) Turn off the mixer and scrape down the hook and the sides of the bowl as necessary. Add the chopped herbs and mix on medium speed until they are distributed throughout the dough, about 2 to 3 minutes.
Move the dough to the oiled rising bucket or mixing bowl and cover. Allow to rise at room temperature (70 to 75° F) until doubled, about 1-½ to 2 hours.
Lay some parchment paper on the pizza peel or baking sheet, then dust the surface lightly with flour. Uncover the risen dough and turn it out onto a lightly floured surface. Cut the dough into 4 equal pieces. Roll each piece into a rope about 14 inches long. Lay two of the ropes side by side and pinch together at one end. Twist the two pieces together like a rope and then pinch the other ends together to seal. Place the shaped loaf on the parchment paper and repeat with the other pieces of dough.
Drape plastic wrap over the shaped loaves and allow to stand at room temperature (70 to 75° F) until they look puffy, about 30 minutes to 1 hour. If you press your finger in the dough, it should spring back slowly.
While the dough rises, about 1 hour before baking, place the baking stone on the middle rack of the oven and the cast-iron skillet on the lower rack. Preheat the oven to 425° F.
Remove the plastic wrap and leave the loaves on the parchment paper. Slide the loaves and the paper onto the heated stone. Put ¼ cup of ice cubes into the cast-iron skillet to produce steam. Bake until the loaves are golden brown, 20 to 30 minutes. (My oven cooked them in 25 minutes.)
Use the pizza peel or baking sheet to remove the loaves from the oven. Cool them on a wire rack for about 30 minutes, and serve warm. To store, allow to cool completely and keep in a resealable plastic bag for up to 3 days. Can be frozen for up to 1 month.