Add the potatoes, carrots, and optional green beans to the slow cooker and season with salt, garlic powder, and onion powder.
In a large bowl, combine the ground beef, onion, parsley, crushed crackers, onion soup mix, eggs, ketchup, milk, Worcestershire sauce, Italian seasoning, garlic powder, and salt.
Shape the meat mixture into a loaf and place it in the slow cooker with the vegetables.
Mix the brown sugar and ketchup and spread over the meatloaf. Cook on LOW for 7-8 hours or HIGH for about 5 hours, until cooked through.