Peel carrots and cut into large chunks, along with the celery. Slice garlic and onion.
Add carrots, celery, garlic, onion, and broth to slow cooker; cook on high for 2-4 hours or on low for 4-5 hours.
Chop mushrooms and green onions; add to slow cooker. Remove carrots and celery, and cut into smaller pieces; add back to slow cooker and cook for an additional hour, checking to be sure mushrooms have become tender.
Meanwhile, prepare salad: In a large mixing bowl, toss together lettuce, tomatoes, dressing, and almonds.
Serve soup with a side salad and a slice of Italian bread.