In the bowl of a stand mixer or a large bowl, add warm water and yeast. Let it sit for 5-7 minutes until the yeast bubbles.

Add olive oil, rosemary, sea salt, and flour to the yeast mixture. Stir until combined.

Lightly oil the insert of a 6-quart slow cooker with cooking spray.

Place dough ball in the center of the slow cooker. Cover with paper towels or a kitchen towel to absorb excess moisture and secure the slow cooker lid. Cook on high for 2.5 hours.

Use an instant-read thermometer to check that the internal temperature is between 200-210°F (93-99°C). The bread should be lightly golden brown, dry on the surface, and sound hollow when tapped on the bottom.

Remove from the slow cooker and transfer to a wire rack. Let the bread cool for at least 1 hour. Slice with a serrated bread knife and serve warm or at room temperature.