This super easy Slow Cooker Spaghetti Squash with Meatballs is just 3 ingredients and takes very little prep work. You can use jarred spaghetti sauce (or homemade marinara) as well as frozen prepared meatballs (or homemade meatballs). Spaghetti squash is a type of garden squash that, when roasted or cooked, the filling resembles spaghetti noodles. …