Slice each zucchini in half lengthwise to create flat, even "steaks". Use a sharp knife to score the flesh side 1/4-inch deep diagonally at 1/2-inch intervals, rotating 90 degrees to create a crosshatch pattern without cutting through the skin. Season the scored sides with kosher salt and let sit at room temperature for 15 minutes to draw out excess moisture.

While the zucchini rests, preheat your oven to 425°F (220°C) with an oven rack positioned in the center. Heat 2 tablespoons of extra-virgin olive oil in a large skillet over medium heat. Add the chopped garlic, red pepper flakes, and dried oregano. Cook for 1 to 2 minutes until intensely fragrant but not browned, then scrape the herbed oil into a small bowl and set aside.

Thoroughly pat the scored zucchini halves completely dry with paper towels, removing all pulled moisture. Wipe out the skillet and heat another 1 tablespoon of olive oil over medium-high heat. Place zucchini halves flesh-side down in the skillet and cook undisturbed for 2 to 3 minutes until a rich, caramelized golden brown color forms. Transfer them skin-side down onto a rimmed baking sheet. Repeat with remaining zucchini halves and the final tablespoon of oil.

Brush the golden, scored sides of the zucchini steaks generously with your reserved garlic-herb oil mixture, letting it sink into the cuts. Bake in the preheated oven for 8 to 10 minutes until the centers are just tender. Remove from the oven and pile the shredded mozzarella and Parmesan cheese evenly on top of each steak. Switch the oven to a high broil, return the sheet to the top rack, and watch closely for 2 to 3 minutes until the cheese is melted, bubbling, and deeply blistered.

Garnish immediately with fresh hand-torn basil or parsley and an extra pinch of red pepper flakes if desired. Serve hot straight from the baking dish!