Prepare the ham: Place the ham flat side down in the slow cooker. If it doesn’t fit perfectly, trim a little from one end.
Make the glaze: In a medium bowl, whisk together the brown sugar, maple syrup, apple cider, Dijon mustard, cloves, cinnamon, and apple cider vinegar.
Pour and cover: Pour the glaze over the ham. Dot the top with butter slices.
Cook low and slow: Cover and cook on LOW for 4 to 6 hours, or until heated through and tender. Baste the ham with the juices once or twice during cooking for a richer glaze.
Thicken glaze (optional): Transfer 1 cup of the cooking liquid to a small saucepan. Simmer for 5–7 minutes until slightly thickened, then drizzle over the sliced ham before serving.
