Set the fully cooked ham into a slow cooker that is at least 6 quarts in capacity.
In a small bowl, whisk together brown sugar, honey, Dijon mustard, ground clove, and ground cinnamon until well blended.
Pour the honey mustard mixture evenly over the ham in the slow cooker.
Cover with the lid and cook on LOW for about 4 to 6 hours or on HIGH for 2 to 4 hours, until the internal temperature reaches 140°F (60°C).
Carefully take the ham out and loosely cover it with foil; let it rest while you prepare the glaze.
Pour the cooking juices into a saucepan and bring them to a low simmer over medium heat.
Mix a little cornstarch with water to create a slurry and add it gradually to the simmering juices, whisking constantly until the sauce thickens.
Brush this thickened glaze onto the sliced ham before serving for extra flavor, if desired.