My slow cooker cook book also says " Because they cook more slowly than meats, generally place fresh vegetables such as potatoes, carrots, celery and onions, in the bottom and around the sides of the slow cooker then place meat on top."
Slow cookers are notoriously slow when cooking vegies and smaller pieces cook faster.
POT ROAST WITH CREAMY MUSHROOM SAUCE
2 TO 2 1/2 lb. boneless beef roast
1 envelopr dry onion soup mix
10 3/4 oz. can cream of mushroom soup
1. Place roast in slow cooker, Sprinkle with the dry soup mix. Top with mushroom soup.
2. Cover. Cook on High 1 hour and then on low 8 hrs., or until meat is tender.
Add cubed potatoes and sliced carrots before adding beef. Proceed with directions above.
Hope this is of some help