For the Preferment:

1. Pour the warm water into a medium bowl and whisk in the yeast. Let the mixture stand for 10 minutes.
2. Stir in the flour with a sturdy spoon and mix until it forms a shaggy dough. Continue to stir until the mixture is smooth and slightly elastic. It will be a little loose.
3. Cover the bowl with plastic wrap, and set aside for 3-4 hours at room temperature, or up to 12 hours in the refrigerator.

For the Bread:

1. Pour the warm water into the bowl of a stand mixer. Add the yeast, whisk by hand to blend, and let the mixture stand for 10 minutes.
2. Fit the stand mixer with the dough hook attachment. Add the preferment and the olive oil and mix on low speed for 1 minute. Add the flour, rosemary, thyme, and salt. Mix on low speed until it comes together in a cohesive mass, about 2-3 minutes. It will look wet and sticky.
3. Cover the bowl with plastic wrap, and let it rest for 20 minutes to allow it to fully hydrate before any further kneading.
4. Turn the mixer to medium-low and continue to mix until the dough is firm, elastic, and smooth, about 5-7 minutes. It will still be soft. Add more flour, one tablespoon at a time, if the dough feels too sticky to work with.
5. Lightly oil a large bowl, and transfer the dough to the bowl, rolling it around in the oil. Cover tightly with plastic wrap and let the dough rise until doubled in size, 1 1/2-2 hours.
6. Turn the dough out onto a lightly floured work surface. Gently press down on the dough to expel some of the air bubbles. Cut the dough in half, and transfer each half to two baking sheets lined with parchment paper or silicone mats. Using your hands, lightly stretch and form the dough into a large leaf shape.
7. Make the design, using a sharp knife to cut slits in the dough to resemble leaf veins: one slit down the center, then two or three slits at an angle on each side of the center. If using silicone mats, be careful to not cut through the material. Gently stretch out each slit to make decorative holes.
8. Cover the dough loosely with plastic wrap, and let the dough proof for 30-40 minutes.
9. While the dough is proofing, preheat the oven to 425°F.
10. Gently brush the surface of the proofed dough with olive oil, and sprinkle salt and chopped herbs on top. Bake for 20-25 minutes, until the bread is golden brown. Transfer to a cooling rack to cool slightly. Serve while still warm.