Preheat the oven to 425 degrees.
Cook the pasta shells until al dente, about 10 minutes. Drain and drizzle with a little olive oil to keep them from sticking together.
In a skillet with olive oil, sautée the spinach until soft. Remove from heat and cool.
Add the spinach to a medium bowl and combine with the crab meat, ricotta cheese, parmesan cheese, minced garlic, oregano, red pepper flakes, salt, and pepper.
Pour the marinara sauce in the bottom of a 9x13 baking dish. Stuff each shell with the seafood filling and line in the pan. Cover with foil and bake for 20 minutes.
Serve with more marinara and top with parmesan cheese. Enjoy!