Combine ground beef, breadcrumbs, egg, garlic, parmesan, red pepper, basil, parsley, sauce, and Worcestershire sauce in a large bowl. Using your hands, mix and knead the meat mixture until fully combined.

Roll the meat into golf ball sized pieces.

Heat a large skillet over medium high heat.

Working in batches, brown the meatballs so they are just brown on the inside - about 30 seconds per side.

Place the browned meatballs into the bowl of your slow cooker and cover with marinara sauce.

Cover and cook on low 6-8 hours.

When the meatballs are done, cook the spaghetti according to package directions and serve topped with the meatballs and marinara.

TO FREEZE: Prepare meatballs and brown them. Let cool. Place meatballs in a gallon sized freezer bag and top with marinara sauce. Remove as much air as possible and seal. Freeze up to 3 months. When ready to serve, defrost overnight or run the bag under warm water to break into pieces and place in slow cooker (it's okay to be partially frozen). Cook on LOW 8 hours.