Add the poolish, flour, salt, and water to the bowl of a heavy-duty mixer fitted with a dough hook. Mix on the lowest speed until the dough is shaggy, about 1 minute. Cover with plastic wrap and let rest for 20 minutes.
Add the yeast to the mixture. Turn the mixer on low and slowly drizzle in the olive oil. Turn the mixer up to medium and continue mixing for 3-5 minutes. Add the herbs, chiles, and olives, and mix until incorporated, about 1 minute. Don't. worry if the olives aren't fully distributed.
Place the dough in a lightly greased bowl, cover with plastic wrap, and let rise at room temperature for 1 hour. Halfway through, punch down the dough and fold the sides over itself. Re-cover the bowl and let rise for the remaining time.
Preheat the oven to 450 F. Line two half-sheet pans with parchment paper and lightly oil the top of the parchment.
Turn out the dough onto a floured surface and knead into a ball. Divide the dough into two and place it on the prepared sheet pans. Using your fingers, flatten each piece into a 12x8-inch oval and then gently stretch the bottom to form a rough triangle. Cover with a kitchen towel and let rest for 10 minutes.
Make two vertical cuts in the center of each oval using a sharp knife or pizza cutter. Reach under the dough and spread it apart to open up the cuts. Then, make six diagonal cuts on each side of the center cuts. Again, reach under the dough and gently spread it outward to form the leaf shape. Let rise uncovered until noticeably puffy, about 20-30 minutes.
Generously coat the dough's surface with olive oil using a pastry brush. Sprinkle with flaky sea salt and black pepper. Bake until golden brown, about 20-25 minutes. Remove the bread from the oven and brush with more olive oil.