In a large bowl, stir together the all-purpose flour, instant yeast, chopped fresh rosemary (if using), and kosher salt. Add the room temperature beer and mix with a spatula until just combined. The dough will be shaggy. Cover the bowl with plastic wrap and let it sit at room temperature for at least 12 hours, ideally overnight (12-18 hours).

After the long rise, preheat your oven to 450°F (230°C). Place a large (5-6 quart) Dutch oven with its lid into the preheating oven and let it preheat for 30 minutes. This is crucial for a crispy crust.

Generously dust a clean work surface with more all-purpose flour. Scrape the sticky, loose dough out of the bowl onto the floured surface. Using floured hands, gently form the dough into a loose ball. Carefully transfer the dough ball onto a piece of parchment paper. Cover it loosely and allow it to rise for another 1 hour, or until it has noticeably doubled in size.

When ready to bake, carefully lift the dough (using the parchment paper as a sling) and gently place it into the preheated Dutch oven. Cover the Dutch oven with its lid.

Bake the bread, covered, for 30 minutes. After 30 minutes, carefully remove the lid and continue baking for another 15-20 minutes, or until the bread has a deep, golden-brown crust.

Carefully remove the Dutch oven from the oven. Using the parchment paper, lift the bread out and transfer it to a wire rack to cool completely before slicing. Enjoy warm with softened butter and a sprinkle of sea salt.