Mix salt, paprika, cayenne pepper, onion powder, thyme, white pepper, garlic powder, and black pepper together in a small bowl.
Rub seasoning mixture over the entire chicken to evenly season. Put rubbed chicken into a large resealable plastic bag; refrigerate 8 hours to overnight.
Remove chicken from bag and cook in slow cooker on Low until no longer pink at the bone and the juices run clear, 4 to 8 hours. An instant-read thermometer inserted into the thickest part of the thigh, near the bone should read 165 degrees F (74 degrees C).