Combine the ground beef, bread crumbs, garlic cloves, parsley, mint, paprika, salt, pepper, and 2 eggs together in a bowl. Form walnut-sized balls. Place balls inside of slow cooker.
Combine the tomato sauce, lemon rind, lemon juice, salt, pepper, and mint leaves. Pour sauce over meatballs. Cover and cook on low for 4-6 hours. Serve with rice.