Spinach and Ricotta Stuffed Shells

18 uncooked jumbo pasta shells (about half of a 12 ounce package)
1 package (15 ounces) ricotta cheese
7 ounces frozen chopped spinach, thawed and squeezed dry
1/2cup granted Parmesan cheese
1 egg, lightly beaten
1 clove garlic, minced
1/2 teaspoon salt
1 jar (24 to 26 ounces) marinara sauce
1/2 cup (2 ounces) shredded mozzarella
1 teaspoon olive oil

1. Cook pasta shells according to package directions until almost tender. Drain well. Combine ricotta cheese, spinach, Parmesan cheese, egg, garlic and salt in medium bowl.
2. Pour 1/4 cup marinara sauce in bottom of slow cooker. Spoon 2-3 tablespoons ricotta mixture into 1 pasta shell and place in bottom of crock pot. Repeat with enough additional shells to cover bottom of crock pot. Top with another 1/4 cup marinara sauce. Repeat with remaining pasta shells, ricotta mixture and marinara sauce. Top with mozzarella cheese. Drizzle with oil. Cover, cook on high 3-4 hours or until mozzarella cheese is melted and sauce is heated through.