Whisk one ¼-oz. envelope active dry yeast (about 2¼ tsp.), 2 tsp. honey, and 2½ cups lukewarm water in a large bowl with lid and let sit 5 minutes (it should foam or at least get creamy).

Add 5 cups (625 g) all-purpose flour and 1 Tbsp. kosher salt and mix with a rubber spatula until a shaggy dough forms and no dry streaks remain.

Pull the dough to the side and pour 4 Tbsp. extra-virgin olive oil around the bottom of the dough. Turn dough to coat in oil. Cover with lid and place in fridge. Chill until dough is doubled in size (it should look very bubbly and alive), at least 8 hours and up to 1 day. If you're in a rush, you can also let it rise at room temperature until doubled in size, 3–4 hours.

Generously butter a 13x9" baking pan, for thicker focaccia that’s perfect for sandwiches, or an 18x13" rimmed baking sheet, for focaccia that's thinner, crispier, and great for snacking. The butter may seem superfluous, but it’ll ensure that your focaccia doesn’t stick. Pour 1 Tbsp. extra-virgin olive oil into center of pan. Transfer dough to prepared pan and gently try to encourage the dough to take the shape of the pan. Pour any oil left in bowl over and turn dough to coat it in oil. Let rise, covered, in a dry, warm spot until doubled in size, at least 1½ hours and up to 4 hours.

Place a rack in middle of oven; preheat to 450°. To see if the dough is ready, poke it with your finger. It should spring back slowly, leaving a small visible indentation. If it springs back quickly, the dough isn’t ready. (If at this point the dough is ready to bake but you aren’t, you can chill it up to 1 hour.) Lightly oil your hands. If using a rimmed baking sheet, gently stretch out dough to fill (you probably won't need to do this if using a baking pan). Dimple focaccia all over with your fingers, creating very deep depressions in the dough (reach your fingers all the way to the bottom of the pan). Drizzle with remaining 1 Tbsp. extra-virgin olive oil and sprinkle with flaky sea salt. Bake focaccia until puffed and golden brown all over, 20–30 minutes.

Hold off on this last step until you're ready to serve the focaccia: Melt 4 Tbsp. unsalted butter in a small saucepan over medium heat. Remove from heat. Peel and mince in 2–4 garlic cloves. Return to medium heat and cook, stirring often, until garlic is just lightly toasted, 30–45 seconds. (Or, if you prefer raw garlic to toasted garlic, you can grate the garlic into the hot butter, off heat, then brush right away.)

Brush garlic-butter all over focaccia and slice into squares or rectangles. Do Ahead: Focaccia is best eaten the day it's made, but keeps well in the freezer. Slice it into pieces, store it in a freezer-safe container, then reheat it on a baking sheet in a 300° F oven.