Place chicken breasts in slow cooker in a single layer for even cooking.
Prepare rice according to package instructions while chicken cooks.
In a medium bowl, whisk buffalo sauce, ranch dressing, and chicken broth until smooth.
Pour sauce mixture over chicken, ensuring all pieces are coated, then add butter on top and cover.
Cook on low for 4-6 hours or on high for 2-3 hours until chicken reaches 165°F and shreds easily.
Let chicken rest 3-5 minutes, then shred directly in slow cooker and stir to coat with sauce.
Assemble bowls with cooked rice, buffalo chicken, cheddar cheese, lettuce, celery, carrots, and optional blue cheese.
Serve immediately while hot.