Add the stock, potatoes, carrots, celery, onion, garlic, thyme, bay leaves, salt, and pepper to a 7 or 8-quart slow cooker. Stir to combine. Cover, and cook on low for 6-8 hours or high 3-4 hours.
8 cups chicken stock, 1 pound yukon gold potatoes, 2 carrots, 2 stalks celery, 1 onion, 3 garlic cloves, 4 thyme sprigs, 2 bay leaves, ½ teaspoon salt, ½ teaspoon ground black pepper