In a large mixing bowl, combine the warm water, honey and yeast. Whisk gently to combine. Let rest for about 5 minutes, until foamy/bubbly. If the mixture doesn't foam or bubble, start over with new yeast, as the yeast is likely dead.
Add the flour, 2 tablespoons of olive oil and 1 teaspoon salt to the bowl. Mix with a rubber spatula or wooden spoon until well combined. Then continue stirring and folding the dough over on itself for 1 minute. The dough will be very sticky.
Cover the bowl with a clean kitchen towel and let the dough rise at room temperature for 1-2 hours, until doubled in size.
Grease the bottom and sides of a 9x13-inch baking pan (a metal pan is best, but glass will also work) with 1 tablespoons of olive oil. Use oiled hands to transfer the dough to the baking pan, spreading the dough out so that it mostly covers the bottom of the pan. If the dough is resistant to stretching out, let it rest for about 10 minutes to relax the dough and then try again.
Cover the pan with a clean kitchen towel and let the dough rise for 45 minutes.
Meanwhile, preheat oven to 425° F.
After the dough has risen for 45 minutes, use oiled fingers to dimple the dough by pressing your fingers down into the dough all the way to the bottom of the pan. Do this in different spots all around the bread. Then drizzle the remaining 1 tablespoon of olive oil over the dough. Sprinkle on the fresh rosemary and flaky sea salt.
Immediately transfer the bread to the preheated oven and bake for 22-26 minutes, until golden brown on top. Let cool for at least 15 minutes before slicing and serving.
Focaccia is best the day it is made but it will still be tasty on the second day.