Place the ham, peppercorns, all spice, onion, carrot, celery, thyme, and rosemary in a slow cooker.
Add enough water to fully submerge the ham. Cover and cook on high for about 2 hours.
Take the ham out of the broth and allow it to cool slightly. Trim off the skin and any extra fat, leaving a thin layer intact. Score the surface into square patterns.
In a bowl, combine all the glaze ingredients and stir until well blended.
Preheat the oven to 380°F. Line a baking dish with foil. Brush half of the glaze over the ham and place it in the prepared dish. Bake for 15 minutes.
Coat the ham with the remaining glaze and continue baking for another 20 minutes.
Remove the ham from the oven and let it rest for about 10 mins before serving.
Notes
To achieve a caramelized crust, broil the ham for the last 5 minutes of baking.
Leftover ham can be stored in an airtight container in the fridge for up to 5 days or frozen for later use.
If serving cold, let the ham cool completely before slicing. Cut into thin pieces and serve.