The night before, mix bread flour, cold water, yeast, and honey to make the starter
Cover the starter and let rest overnight on the countertop
The next day, mix in the starter, remaining flour, room temperature water, salt, and extra virgin olive oil using a fork or hands
Cover and let rest for 30 minutes
Perform stretch and folds by grabbing the dough, stretching it out, and folding towards the center
Repeat stretch and folds 3 times every 15-20 minutes
Place the dough in a 9x5 inch metal loaf pan lined with parchment paper and greased with extra virgin olive oil
Let the dough rest for 1.5-2 hours covered
Preheat oven to 420°F
Grease your fingertips with extra virgin olive oil and create dimples in the focaccia
Add flaky salt and bake for 6 minutes on the bottom rack
Remove from oven, add fresh rosemary, and bake for an additional 8-10 minutes on the middle rack until golden
Remove immediately onto a baking rack and let cool for 10 minutes before cutting
