In the bottom of a stand mixer bowl, stir water together with yeast and honey until dissolved. Set aside to proof 10 minutes; it should look foamy and bubbly.
Add in 2 tablespoons olive oil and 2 cups flour. Stir together to form the dough (with a dough hook). Stir in salt. Slowly incorporate the flour to the dough bit by bit until dough is gathered on the dough hook and have (mostly) cleaned the sides of the bowl. Be aware that you may not use all the flour listed or you may need a little more. When you touch the dough, it should feel tacky but not stick to your hands. This is a good indicator that dough is done.
Coat dough in olive oil and set aside to rise 1 hour.
Pour half of the olive oil (1/4 cup) onto the bottom of a half sheet pan*. Press out into an even layer across the entire baking pan and using your fingertips, create indentations across the entire layer of dough. Drizzle with remaining olive oil. Cover and rise another hour or until doubled in size.
Preheat oven to 400 degrees. Sprinkle focaccia with chopped fresh rosemary and coarse sea salt. Bake 15-20 minutes or until golden brown. Cool before cutting into pieces and serving.
*if you want a thicker focaccia, you can easily use a 9x13 pan in place of the half sheet pan. You will just want to bake at 375 degrees for 25-30 minutes OR until baked completely.