Add 6 cups apple cider to crockpot. Stud orange slices from 1 Valencia orange with 20 whole cloves and add them to the crockpot along with the 4 cinnamon sticks. Set temperature to high and heat for at least an hour.
To serve, add 6 ounces whiskey to the slow cooker. Alternatively, you can keep the warm apple cider in the slow cooker non-alcoholic and just add individual shots of whiskey to a mug and then fill with the spiced cider. Top with whipped cream and sprinkle with pumpkin pie spices.