- Place starter, water, and 20 grams oil in large bowl and stir to combine.
- Add flours and mix with hands until all is hydrated and no lumps remain. Cover with plastic and let rest for 20 minutes.
- Sprinkle salt over dough and mix thoroughly in with hands, making sure salt is completely incorporated. Cover and allow to bulk proof for 2 hours, turning and folding every 30 to 45 minutes. Cover with towel and then plastic and refrigerate 8 to 12 hours.
- Remove dough from refrigerator and turn out onto well-floured surface. Gently pat into large rectangle, careful not to deflate dough. Cut in half using bench knife and transfer to parchment-lined baking sheet.
- Using fingertips, make indentations in dough (these will act as wells for oil). Drizzle remaining oil over dough and then sprinkle on za’atar. Layer lemon slices on top and finish with capers. Cover loosely with plastic. Allow to final proof at room temperature for about 1 to 1½ hours, until puffy and expanded. Preheat oven to 450 degrees as bread proofs.
- Bake fully proofed loaves for 25 to 28 minutes, rotating halfway through to ensure even baking. When edges are golden and crispy, remove from oven and transfer loaves to wire rack. Garnish with fresh herbs and flaked sea salt. Serve warm or at room temperature.