Cover shrimp and scallops with water and sprinkle with ¼ tsp salt. Let the seafood brine for 15-30 minutes.
Preheat oven to 350 F.
Cook shells according to package directions. Drain. Toss with olive oil if you're not ready to start stuffing so they won't stick together.
Mix together remaining ¼ tsp salt, ricotta, Parmesan, garlic, parsley, black pepper, and red pepper flake.
Drain seafood and pat dry (do not rinse). Chop shrimp into pieces about the size of a bay scallop. Add to a skillet with 1 TBS butter, and cook until opaque, 3-5 minutes. Remove seafood from skillet with a slotted spoon and mix into the ricotta mixture.
Pour marinara into a 9x13 inch glass baking dish, and spread it out to cover the bottom.
Fill each shell with the ricotta-seafood mixture and place into the marinara in the baking dish.
Cover the baking dish with foil and bake for 20 minutes. Remove foil and bake another 10 minutes.
Let cool 5-10 minutes before serving.
Recipe by Alison's Allspice at https://www.alisonsallspice.com/seafood-and-ricotta-stuffed-shells/