Stir the yeast and sugar into the 1½ cups water at about 105°F. Leave for 10 minutes; proceed when the surface becomes foamy.

Add the bread flour, salt, finely chopped rosemary, and ¼ cup olive oil. Stir and scrape until a shaggy, sticky dough forms. If flour remains dry, mix in additional water 1 tablespoon at a time, up to 2 tablespoons.

Line the Instant Pot insert with parchment and lightly oil the paper. Add the dough and cover loosely with a glass lid. Select yogurt Normal, without pressure, for about 4 hours or until the dough has expanded substantially and shows bubbles. Do not use sauté or yogurt Boil.

Lightly flour a work surface, turn out the dough, and fold its edges toward the center to form a round. Place on fresh parchment rated for 450°F and cover loosely for 30 minutes. Meanwhile preheat the oven and a lidded 3½–5-quart Dutch oven to 450°F, checking all cookware temperature limits.

With dry mitts, remove the heated pot and lid. Score the loaf about ½ inch deep, carefully lower it into the pot, and replace the cover. Bake on the middle rack for 30 minutes.

Uncover and continue baking for 10–15 minutes until deeply golden, with a fully baked center around 200–210°F. Lift out carefully and cool uncovered on a rack for at least 60 minutes before cutting.