In a large bowl, whisk together the all-purpose flour, granulated sugar, instant yeast, and salt. Pour in the warm water and olive oil. Stir with a wooden spoon until a shaggy dough forms.
Turn the dough out onto a lightly floured surface and knead for 5 to 6 minutes until the dough is smooth and elastic. If the dough is too sticky, add a tiny bit more flour a teaspoon at a time.
Place the dough in a lightly oiled bowl, cover with a clean towel or plastic wrap, and let it rise in a warm spot for 45 to 60 minutes, until it has doubled in size.
Gently punch down the risen dough and shape it into a round loaf that will fit inside your air fryer basket. If you have a 6-inch round air fryer-safe pan, lightly grease it and place the dough inside. Otherwise, shape the dough and place it on a piece of parchment paper. Let it rest for 15 minutes while it puffs up slightly.
Preheat the air fryer to 330 degrees F. Brush the top of the loaf lightly with olive oil. Place the bread in the air fryer basket.
Air fry at 330 degrees F for 18 to 22 minutes, until the loaf is deeply golden brown on top and sounds hollow when you tap the bottom. If the top browns too quickly, loosely cover with a small piece of foil for the last few minutes.
Remove the bread from the air fryer. Brush the top immediately with melted unsalted butter and sprinkle with flaky sea salt if desired. Let the bread cool on a wire rack for at least 10 minutes before slicing.