Slow Cooker Vegetable Beef Barley Soup

stew beef (cut into 1-inch chunks)

salt and freshly ground black pepper

slow cooker beef bone broth (or commercial beef stock or broth)

ribs celery (chopped)

large onion (chopped)

garlic (chopped)

potatoes

carrots (chopped, and peeled if you prefer)

mushrooms (sliced)

pearl barley