Bloom your yeast. To bloom, place your warm water into your mixing bowl, and sprinkle your yeast on top. Wait until the yeast looks foamy, and the water looks murky. Once bloomed, add all of the rest of your ingredients to the mixing bowl. See notes.
Once you have added all of your ingredients to your bowl, start the mixer on low to incorporate all of your ingredients. Once your dough comes together, turn your mixer to medium-high speed and mix for about a minute. When the dough stops sticking to the side of the bowl and starts to make a smacking sound, it is time to move on to the next step. If it is still sticking to the sides of the bowl, again, run your mixer on medium-high for 30 more seconds.
In a 9x13 glass pan: grease the pan with two tablespoons of olive oil and scoop your dough into the pan. Spread out dough with your fingers. It will be sticky.
Once it’s spread out, cover with plastic wrap and place in a warm area. A good trick is to pre-heat the oven (350°F), while your bread is in the mixer, then when your bread is ready for proofing, place it on top of the oven and let the ambient heat proof it. If you choose not to do this, preheat your oven (350°F) when your bread has been proofing for about 45-50 minutes. Your bread will be proofed when it has doubled in size.
Once your bread has proofed, take your fingers and poke holes into your dough. Then, take your remaining two tablespoons of oil and drizzle over the top of your focaccia. Sprinkle with the sea salt and the fresh rosemary.
Bake for 20 minutes, and then rotate. Bake for another 20 minutes. Check to see if its done (see notes). If it needs more time, bake it for five more minutes, then check again.