Spelt Rosemary Olive Sourdough Boule

Steps

1. Starter timing: in the morning, give your sourdough starter its usual feeding (equal weights of fresh feed and water) and leave it at about 75°F (24°C); it should double and peak, bubbly and domed, in 4 to 6 hours. Use the sourdough starter at its peak.
2. Prepare the add-ins before mixing: halve the olives and pat them dry, and crush the rosemary between your fingers. Set aside about one quarter of the rosemary for the top; the remaining three quarters goes into the dough.
3. In a large bowl, mix the spelt flour and the bread flour with 320 g of the water (all but 20 g) until no dry patches remain. Cover and rest 30 minutes (autolyse).
4. Add the sourdough starter to the dough and squeeze it in with wet hands until even. Sprinkle the salt over the dough, add the reserved 20 g of water and half the olive oil, and squeeze and fold until absorbed. This is about 70% hydration and 2% salt.
5. Bulk rise at about 75°F (24°C), covered, for 4 to 5 hours. Every 30 minutes for the first 2 hours, do a set of stretch-and-folds (4 sets total). On the second set, scatter the olives and the three quarters of the rosemary over the dough and fold them in. Spelt dough is delicate, so fold gently.
6. Bulk is done when the dough has risen about 50%, looks domed and airy with bubbles at the sides, and jiggles when the bowl is shaken.
7. Dust the counter lightly with a little extra bread flour, turn out the dough, pre-shape into a loose round, rest 20 minutes, then shape a tight boule. Place it seam side up in a banneton or towel-lined bowl dusted with a little more bread flour.
8. Cover and cold proof in the fridge for 12 to 14 hours.
9. Place a Dutch oven with its lid in the oven and preheat to 475°F (245°C) for 45 minutes.
10. Turn the cold dough onto parchment, score a cross on top, brush with the remaining half of the olive oil, pressing a few fingertip dimples around the cuts focaccia-style, and sprinkle on the reserved quarter of the rosemary.
11. Lower the boule into the hot Dutch oven, cover, and bake 20 minutes. Uncover, reduce to 450°F (230°C) and bake 25 to 30 minutes more, until the crust is deeply browned and the center reads 205°F (96°C).
12. Cool the loaf on a rack for at least 2 hours before cutting into 12 slices.