Creating your Zucchini Pizza Casserole is quite simple if you follow these outlined steps:

1. Preheat Oven: Preheat your oven to 375°F (190°C).

2. Prepare Zucchini: Slice the zucchinis thinly. Place them in a colander and sprinkle with salt. Let them sit for about 10-15 minutes to release excess moisture.

3. Cook the Meat: In a large skillet, heat a drizzle of olive oil over medium heat. Add the diced onion and minced garlic, sautéing until fragrant. Add the ground beef and cook until browned. Drain any excess fat.

4. Mix in Sauce: Pour the marinara sauce into the skillet with the cooked meat. Stir in Italian seasoning, salt, and pepper. Let the mixture simmer for about 5 minutes to enhance the flavors.

5. Layer Ingredients: In an olive oil-greased baking dish, layer half of the zucchini slices at the bottom. Next, pour half of the meat sauce mixture over the zucchini. Follow this with a layer of half the shredded mozzarella cheese.

6. Repeat Layers: Add the second half of the zucchini and repeat the process with the remaining meat sauce and cheese.

7. Add Parmesan: Top the casserole with grated Parmesan cheese for an extra flavor boost.

8. Bake: Place the casserole in the preheated oven and bake for 30-35 minutes, or until the cheese is bubbly and golden brown.

9. Cool and Garnish: Once done, remove the casserole from the oven and let it cool for a few minutes. Garnish with fresh basil and red pepper flakes if desired.