In the bowl of a stand mixer fitted with the paddle attachment, whisk together 3/4 cup (180g) warm water and Platinum Instant Sourdough Yeast by hand until dissolved. Add 1 1/3 cups (169g) flour, and beat at low speed until combined, about 30 seconds. Cover and let rise in a warm, draft-free place (75°F/24°C) until doubled in size, 30 to 45 minutes.
Add salt, garlic powder, rosemary, sage, thyme, black pepper, remaining 2 2/3 cups (339g) flour, and remaining 1/2 cup (120g) warm water to yeast mixture, and beat at low speed until dough comes together, about 30 seconds. Switch to the dough hook attachment. Beat at low speed for 2 minutes. (Dough will appear rough rather than smooth at this point.)
Lightly oil a large bowl. Place dough in bowl, turning to grease top. Cover and let stand in a warm, draft-free place (75°F/24°C) until smooth and elastic, about 1½ hours, turning every 30 minutes. (To complete a turn, grab underside of dough, stretch it up, and fold it to center of dough. Do this four times around the bowl.)
Turn out dough onto a very lightly floured surface, and divide in half. Gently pat one half into a 9x4-inch rectangle; fold one short side over center third, pinching to seal. Fold remaining third over folded portion, pinching to seal. Turn dough over so it is seam side down. Cover and let stand for 20 minutes. Repeat with remaining half of dough.
Line a rimmed baking sheet with parchment paper, letting excess extend slightly over sides of pan. Dust heavily with flour.
Gently pat each baguette into an 8x6-inch rectangle, one long side nearest you. Fold top third of dough to center, pressing to seal. Fold bottom third over folded portion, pressing to seal. Fold dough in half lengthwise so long edges meet. Using the heel of your hand, firmly press edges to seal. Roll into a 15- to 16-inch log of even thickness, tapering ends slightly. (Logs will shrink afterward.)
Place 1 log on prepared pan, seam side down, nestling it against one long side of pan. Pull up and fold parchment to create a wall on opposite side of log. Nestle remaining log on other side of parchment wall, seam side down. Repeat pulling and folding process with parchment to form a wall on opposite side of second log, and weigh down with a kitchen towel to prevent parchment from sliding. Cover and let rise in a warm, draft-free place (75°F/24°C) until slightly puffed, 45 to 50 minutes. (Alternatively, cover and refrigerate for 8 hours or overnight. Let rise in a warm, draft-free place (75°F/24°C) until slightly puffed, 45 to 50 minutes. Shape and bake as directed.)
Place a large cast-iron skillet on bottom rack of oven and a rimmed baking sheet on center rack. Preheat oven to 475°F (250°C).
Carefully transfer dough logs to a sheet of parchment paper; thoroughly dust tops with flour. Using kitchen scissors, make a quick, clean 45-degree cut about 1½ inches from end of 1 log, cutting about three-fourths of the way through. (Be careful not to cut all the way through dough.) Gently turn dough piece to one side. Make a second cut 1½ inches from first, and gently turn dough piece to opposite side. Repeat until you reach end of log, creating a wheat stalk shape. Repeat procedure with remaining log.
Remove preheated pan from oven. Carefully place parchment with dough on pan, and return to oven. Carefully pour 1½ cups boiling water into preheated skillet. (This will create a lot of steam, so wear oven mitts.) Immediately close oven door.
Bake until golden brown and an instant-read thermometer inserted in center registers 205°F (96°C), about 15 minutes. Let cool on pan on a wire rack. Serve with herbed olive oil.