Prepare ham: If needed, score the surface of the ham in a diamond pattern. Optional: stud with whole cloves.
Mix glaze: In a bowl, combine maple syrup, brown sugar, Dijon mustard, pineapple juice, cinnamon, cloves, and nutmeg. Stir until smooth.
Layer in slow cooker: Place pineapple slices at the bottom of the crockpot. Place ham on top. Pour glaze over ham, reserving a few tablespoons for basting later.
Slow cook: Cover and cook on low for 4–6 hours or high for 2–3 hours. Baste ham with glaze every 60–90 minutes for maximum flavor.
Optional caramelization: About 15–20 minutes before serving, remove ham from crockpot and place on a baking sheet. Brush with remaining glaze and broil in oven at 400°F (200°C) until caramelized and golden.
Serve: Transfer ham to a serving platter, garnish with pineapple slices and fresh parsley or rosemary.