Sprinkle rice into bottom of slow cooker. Add onion, carrots, celery and mushrooms. Remove skin from chicken pieces and trim rib bones from the breastbone. Place chicken pieces over vegetables; add broth and 4 cups water. Add poultry seasoning, 1/4 teaspoon of the salt and the pepper.
Cover and slow cook for 6 hours on HIGH or 8 hours on LOW. Carefully remove chicken to a cutting board; discard bones. Shred or chop chicken; return to slow cooker and add remaining 3/4 teaspoon salt. Serve warm.
