Place chicken in the bottom of a slow cooker. Season with salt and pepper and drizzle with olive oil. Spoon pumpkin butter over the chicken. Cover and cook for 4-5 hours on low or 2-3 hours on high (my slow cooker cooks quickly; if yours is not as hot, it might take longer).
Once the chicken is cooked, use two forks to shred the chicken.
Toss apples, coleslaw mix, honey, apple cider vinegar, mayo, and celery seeds together. Salt and pepper to taste.
Warm Yellow Corn Tortillas according to the directions on the back of the package. Fill each with pumpkin butter chicken and apple slaw.
Serve and enjoy!