In a large mixing bowl, combine the the flour, salt, and instant yeast with a rubber spatula. Add lukewarm water. Mix the dough together until the liquid is absorbed and the ingredients form a sticky dough.
3½ cups all purpose flour, 2 teaspoon kosher salt, 2 teaspoon instant yeast, 2 cups lukewarm water
Drizzle the top of the dough with some olive oil and use your hands to rub it all over the surface and sides of the bowl. There is no need to measure here, you simply want to use enough so that everything is thoroughly coated to prevent sticking and a dry crust forming. Cover the bowl with plastic wrap and refrigerate for 12-18 hours.
Meanwhile, combine ½ cup olive oil, garlic cloves, and a 3-4 inch sprig of fresh rosemary leaves in a small saucepan. Heat the mixture over med-low heat for 5-7 minutes, until the oil is warm but not simmering. Remove the pan from the heat and allow the oil to steep for 5 minutes, then remove the garlic and herbs (or pour it through a sieve). Set aside to cool.
½ cup olive oil, 3-4 whole garlic cloves, 3-4 inch sprig fresh rosemary
When you are 3.5-4.5 hours away from eating, remove the dough from the fridge. It should be puffy, risen, and may have some bubbles on the surface. Use two forks to release the dough from the sides of the bowl, pulling it towards the center and rotating the bowl in small turns as you go, until the dough is a rough ball. It will have deflated some during this process, but stop once the sides are released to avoid overdoing it.
Line a non-stick 9x13 pan with parchment paper, then grease the sides and bottom generously with more plain olive oil (I use a paper towel to help rub it around). After it is greased, measure 2 tablespoons of the flavored garlic oil into the bottom of the pan.
Place the ball of dough in the center of the pan, then roll it around gently to coat it thoroughly on all sides, keeping the ball shape as much as possible. Be careful not to over-handle it or it will deflate more. Allow it to rise uncovered at room temperature for 3-4 hours for the final rise. It should puff up and mostly fill the pan all by itself.
After 3-4 hours, preheat the oven to 425°F. While the oven is heating, pour 2 more tablespoons of the garlic oil on the top. Grease your hands with a bit as well, then use all of your fingers to press straight down into the dough, creating dimples and spreading it to the edges of the pan. You can use your fingers to gently stretch it to the edges if needed, but be very careful not to lift it or overly deflate the corners. Sprinkle the top with 1 teaspoon of fresh rosemary leaves and ¼ teaspoon of flaky sea salt. ¼ teaspoon flaky sea salt, 1 teaspoon fresh rosemary leaves
Bake the bread on the middle rack of your oven for 25-30 minutes, until the bottom is golden and crispy. Remove it from the oven and place onto a cooling rack for about 10 minutes.
Remove the warm loaf onto a cutting board and cut into squares or long strips with a serrated bread knife. Serve warm and enjoy!