Using a serrated bread knife, slice the French bread loaf in half lengthwise from end to end. Place both halves cut-side up and cut each half crosswise into two equal pieces, giving you 4 individual pizza portions total (about 5 to 6 inches / 12 to 15 cm long). Trim pieces if needed to fit comfortably in your air fryer basket with a small gap between each one.
In a small bowl, combine 2 tablespoons (30 ml) olive oil with 1/4 teaspoon (0.5 g) garlic powder and 1/4 teaspoon (0.5 g) dried oregano. Stir well until the garlic powder is fully incorporated.
Using a pastry brush or the back of a spoon, spread the seasoned olive oil evenly across the cut surface of each bread piece, coating all the way to the edges. Use a thin, even layer.
Preheat your air fryer to 375°F (190°C) for 2 to 3 minutes. Place 2 pieces of bread in the air fryer basket, cut side up, leaving a small gap between them. Air fry for 3 minutes until the cut surface is lightly golden and starting to feel firm. Remove and set aside. Repeat with the remaining 2 pieces.
Spoon about 2 tablespoons (30 ml) of pizza sauce onto the toasted surface of each bread piece. Using the back of the spoon, spread the sauce in an even layer all the way to the edges, leaving just a thin border (about 1/4 inch / 6 mm) around the perimeter.
Sprinkle approximately 1/3 cup (38 g) of shredded mozzarella cheese evenly over the sauce on each piece. If using sliced fresh mozzarella, place 2 to 3 thin slices across each piece, overlapping slightly. Sprinkle 1/2 tablespoon (2.5 g) of freshly grated Parmesan cheese over each piece.
Arrange 7 to 9 pepperoni slices in a single layer over the cheese on each bread piece. If using shredded mozzarella, place the pepperoni on top of the cheese (not underneath) to weigh it down. Press the pepperoni gently down into the cheese so they adhere slightly.
Carefully place 2 assembled pizzas back into the air fryer basket, cut side up, with a small gap between them. Air fry at 375°F (190°C) for 5 to 7 minutes, until the cheese is fully melted, the pepperoni edges are just starting to curl and crisp, and the crust is golden and firm. Repeat with the remaining 2 pizzas.
Remove the pizzas from the air fryer using tongs and let them rest on the cutting board for 1 to 2 minutes. Sprinkle each pizza with a pinch of Italian seasoning and add any optional garnishes (red pepper flakes, fresh basil, or dried parsley). Slice each piece in half or serve whole, and enjoy immediately.