Pour the apple cider into a slow cooker. Press 2 cloves into each apple quarter. Add the apples, maple syrup, lemon juice and lemon halves and the Fall Spice Mix. Stir to combine. Cover and cook on low for 4 hours.
Discard the apples and lemons. Stir in the bourbon if using. Serve warm, in mugs.
Fall Spice Mix:
Whisk together the cinnamon, pepper, cardamom, nutmeg and salt in a small bowl. The mixture will keep in an airtight container for up to 6 months.