In a medium to large bowl, mix together the flour, 1-1/2 tsp of sea salt, 1-1/2 tsp of dried rosemary leaves and active dry yeast. Add in the water and mix until well incorporated.
Cover the bowl tightly with plastic wrap and let sit at room temperature for 12-18 hours.
After 12-18 hours of letting the dough sit and rise, put the dutch oven with lid on into the cool oven and then preheat to 450 degrees F. You will want the dutch oven to reach 450 degrees before adding the dough.
Once the oven has reached 450 degrees, remove the dutch oven and lid and place the dough into the dutch oven. To prevent the bread from sticking, sprinkle a little bit of flour into the bottom of the dutch oven and continuously add flour to your hands as you form the dough into a round shape.
After the dough is added to the dutch oven, sprinkle the remaining rosemary leaves and sea salt over the top of the dough.
Bake with the lid on for 30 minutes and then after 30 minutes remove the lid and bake for an additional 10-15 minutes until it's nice and brown on top.
Remove the bread from the dutch oven and let cool before serving.