Preheat the oven to 375℉, grease a 2-quart baking dish very lightly with olive oil, spread ½ cup of spaghetti sauce on the bottom of the dish, and set aside.
Bring a large pot of water to a rapid boil to cook the shells. Once the water is boiling, heavily salt the water, and add in the shells. Cook for 9 minutes, or 2 minutes less than the package directions state. Drain the pasta, but do NOT rinse, and allow the shells to cool slightly.
While the pasta is cooking, prepare the stuffing for the shells, by mixing ricotta egg, parmesan, garlic, parsley, red pepper flakes, oregano, salt, and pepper in a medium mixing bowl. Set that aside to stuff the shells.
Once the shells are cool enough to handle, stuff each shell with the ricotta mixture, about ¼ cup filling per shell. Remember to not overstuff the shells, so that the shells can somewhat close around the ricotta filling. Place each stuffed shell into the prepared baking dish.
Top the shells with the remaining spaghetti sauce and then cover with the mozzarella cheese.
Bake for 30 minutes, or until cheese is melted and browned.
Let sit for 5-10 minutes prior to serving.
