Into a large mixing bowl, add warm water and yeast. Allow to stand 5-7 minutes, until the yeast begins to bubble.
To the yeast mixture, add olive oil, rosemary, sea salt, and all-purpose flour. Stir to combine.
Using a dough hook attachment on a stand mixer or your very clean hands, knead the dough until soft and elastic.
Lightly oil your slow cooker.
Place bread dough in the center of the pot.
Cover and cook on high for 2 1/2 hours.
Lift the lid a few times during cooking to release the steam.
An instant-read thermometer inserted deep into the loaf should read between 200 and 210 degrees F (93 to 99 degrees C).
The surface of the bread should be dry and no longer spongy.
Remove the loaf and tap the bottom; it should sound hollow.
Remove rosemary bread from the slow cooker.
Transfer to a wire rack and let cool completely before slicing, at least 1 hour.
Serve warm or room temperature.