In a large mixing bowl, combine the ground beef, breadcrumbs, Parmesan cheese, parsley, eggs, minced garlic, salt, black pepper, oregano, and basil. Mix until well combined.
Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper (optional).
Form the mixture into meatballs, about 1 to 1.5 inches in diameter, and place them on the prepared baking sheet.
Bake the meatballs in the preheated oven for 15-20 minutes until they are browned and cooked through.
Transfer the baked meatballs to the crockpot and pour the marinara sauce over them.
Cover the slow cooker and cook on low for 6 hours or on high for 3 hours.
Once cooked, stir gently to coat the meatballs in the sauce before serving. Serve with pasta, sub rolls, or on their own!