Prep/Fold the Dough

1. Pour a 1/2 cup of the warm water into a large bowl. Sprinkle yeast on top. Place the bowl in a warm place for about 10-15 minutes. Be patient! If yeast is activated, you will see foam on top of the mixture, and even a few small bubbles. Also, if you take sniff, it will smell very much like yeast.
2. Gently stir in sourdough starter, flour, and salt.  Add the other 1/4 cup of water and mix until just combined into a sticky, shaggy dough. Cover with a towel and let rest for 45 minutes.
3. This step includes 4 repetitions of "folding" and "resting" for a total of 3 hours resting time: Instead of dusting your hands with flour, wet your hands with a little water and "fold" the dough: Leaving the dough in the bowl, stretch one side of the dough up and then over the top of the dough. Turn the dough 90 degrees and repeat until you've done each side. Flip the dough over, cover, and let rest another 45 minutes. Repeat this folding and resting process 3 more times.

Shape the Dough

1. After the fourth resting period is done, take the dough out of the bowl and place on a lightly floured surface. Cut the dough into 4 equal pieces. If you have a scale, use it to weight each piece to make sure each is the same amount.
2. Shape each piece into a rectangle and gently stretch out the ends. Cover with an oiled piece of plastic wrap and let rest for 10 minutes.
3. After resting, sprinkle each rectangle with a little bit of flour, a very light dusting so your hands don't stick. Fold each rectangle in half lengthwise and flip over seam side down. Gently roll each piece into a roughly 15 inch long log about 1 1/2 inches in diameter. Gently stretch out the ends again and using your fingertips press them together into a point, forming the baguette shape.
4. Gently move the baguettes onto a bakers couche or make your own using a lightly floured towel (I used a large tea towel): using the towel, create a ridge between each baguette (think taco stand). This will make sure the baguettes maintain their shape while you let them rest for the final time. Cover with an oiled piece of plastic wrap and let rest for 30 minutes.

Bake the Baguettes

1. While the baguettes are resting, turn your oven on to preheat to 450˚F. During the last 10 minutes of rest time, place a pan on the bottom rack of the oven and fill with boiling water.
2. Prepare a baking sheet with parchment paper. VERY carefully move each baguette on to the tray. Spray each baguette with a little water. Dust the tops lightly with flour. Score each one with 4 to 5 overlapping lines about 1/4 inch deep.
3. Being careful of the steam, open the oven and place the tray with the baguettes on the center rack. Spray  a little more water into the oven to make sure there is enough steam.
4. Bake for 16-18 minutes, rotating halfway through, until baguettes are a deep golden brown and sound hollow when the bottom is tapped. Take care not to overcook or you'll use the soft center!
5. Remove the baguettes to a wire rack to cool. Slice and enjoy!