In a large mixing bowl, combine 4 cups of all-purpose flour, 1/4 cup of granulated sugar, 2 teaspoons of salt, and 2 teaspoons of instant yeast. Gradually stir in 1 and 3/4 cups of warm water and 1/4 cup of high-quality olive oil until a sticky dough forms.

Turn the dough out onto a floured surface and knead for about 5 minutes, until it's smooth and elastic. Then, place it in a greased bowl, cover with a clean kitchen towel, and let it rise in a warm place for about 1 hour, or until it has doubled in size.

While the dough is rising, prepare the cinnamon filling. In a small bowl, mix together 1/2 cup of brown sugar and 2 tablespoons of ground cinnamon until well combined.

After the dough has risen, gently punch it down to release the air. Transfer it to a floured surface and roll it out into a rectangle approximately 12x18 inches. Evenly sprinkle the cinnamon mixture over the surface of the dough.

Starting from one long edge, roll the dough tightly into a log shape. Slice the log into 12 equal pieces and arrange them cut-side up in a greased baking pan. Cover the pan with a towel and let the dough rise for about 30 minutes.

Preheat your oven to 375°F (190°C) while the dough is rising for the second time. Bake for 25–30 minutes, or until the edges are golden brown and the top sounds hollow when tapped.

Once baked, remove the focaccia from the oven and let it cool in the pan for 5 minutes. Carefully transfer it to a wire rack to cool slightly before serving warm.