Preheat your oven to 450°F (232°C). Place the sheet pan inside while the oven heats to help the bottom of the crust crisp up.
In a medium skillet over medium heat, crumble the Italian sausage.
Add fennel seeds, garlic powder, oregano, and black pepper.
Cook for about 6–8 minutes, until browned and fully cooked. Drain excess fat and set aside.
Prepare the dough by lightly flouring a surface and rolling or stretch your pizza dough to roughly fit your 9x11 in-h pan.
Carefully remove the hot pan from the oven and drizzle with olive oil.
Transfer the dough into the pan and gently press it out to the edges.
Spread pizza sauce evenly over the dough.
Sprinkle garlic powder and oregano over the sauce.
Add shredded mozzarella evenly across the surface.
Distribute cooked Italian sausage and layer pepperoni slices over the top.
Bake for 18–20 minutes, or until the crust is golden and crisp and cheese is bubbling.
Sprinkle grated Parmesan and red chili flakes to taste.
Let cool slightly, then slice into 12 squares and serve hot!