Combine 8 ounces of your warm water (110ºF or 43ºC), yeast, and sugar and set it aside for 5 minutes or until it’s foamy.
Put your yeast mixture and one cup of flour into the bowl of your Bosch stand mixer with the dough hook attached. Mix to combine. You can use a bowl and a spoon and then knead it by hand if you want to, but it will just take longer. Next add in the rest of your water, the olive oil, and the salt, and mix to combine.
Then, keep adding in the rest of your flour while mixing on low until your dough starts pulling away from the sides of the bowl.
Take the sticky dough out of the bowl and finish kneading it on the table with a tiny bit of flour until the dough looks smooth and bounces back when you touch it with your finger.
Next, put the dough into a bowl greased with olive oil.
Cover the bowl with plastic wrap, and place the covered bowl in a warm area for 1-2 hours or until the dough has doubled in size. I put my bread in my oven turned OFF with just the light on to proof my bread, or in a proofing drawer.
Then, prepare your baking pan by covering the bottom of the pan with a thin layer of olive oil. I know this looks like a lot but trust me, you need it. You want it to be a swimming pool of oil!
Take your very soft dough out of the bowl and stretch it with your hands to make it longer.
Next, place it into the pan with the oil and use your hands to stretch it out to the edges. If the dough shrinks back, let the dough rest for 20 minutes then come back and stretch it some more. Letting the dough rest relaxes the gluten and keeps it from shrinking. Keep doing this until you can get the dough all the way to the edges of the pan.
Cover the pan with some plastic wrap and put it in the fridge overnight. The yeast will continue eating those sugars and rise very slowly. The next day, you should have some nice bubbles on top of the dough.
Preheat your oven to 450ºF (232ºC) and take your dough out of the fridge.
Use your fingers to pop the big bubbles and press dimples into the surface of the dough.
Drizzle olive oil onto the top of the dough so that it settles in those dimples.
Sprinkle a healthy amount of flakey sea salt and chopped rosemary on top of the dough.
Bake the dough in a preheated oven (450ºF or 232ºC) on the middle rack for 25 minutes or until it’s golden brown!
Finally, brush the baked focaccia with more olive oil before serving.