Shrimp is added to this easy slow cooker marinara sauce near the end of the cooking time. Use peeled and cooked shrimp or frozen cooked shrimp which has been thawed. It's a basic marinara mixture flavored with fresh or dried basil and optional oregano. We always add crushed red pepper flakes to the pasta sauce, but that's optional. The marinara is served with hot cooked spaghetti or angel hair pasta. Or serve it over polenta or bow tie pasta.