Prepare the Oven & Spinach:
Preheat the oven to 425°F. Place spinach in a steamer basket over simmering water. Steam for about 1 minute until wilted. Transfer to a strainer, squeeze out excess liquid, and chop finely.

Cook the Pasta Shells:
Bring a large pot of salted water to a boil. Cook the shells for about 10 minutes or until al dente. Drain and drizzle lightly with olive oil to prevent sticking.

Make the Filling:
In a mixing bowl, combine the chopped spinach, ricotta, pecorino, garlic, lemon zest, oregano, red pepper flakes, sea salt, and black pepper. Stir until creamy and well blended.

Assemble the Dish:
Spread the marinara sauce evenly across the bottom of a 9×13 baking dish. Stuff each shell generously with the spinach-ricotta mixture and arrange them in the dish on top of the sauce.

Bake:
Cover the dish with foil and bake for 20 minutes. Remove from the oven, garnish with parsley, and serve warm with extra marinara if desired.