Place the ham flat side down in the slow cooker, ensuring it fits snugly.
If your ham is not spiral-sliced, you can make shallow slices across the surface where you would normally carve it, or score the surface in a crisscross pattern. Either method will help the glaze seep into the meat for extra flavor.
Combine pineapple juice, orange juice, brown sugar, honey, Dijon mustard, cinnamon, and cloves in a small saucepan. Whisk together and bring to a gentle simmer over medium heat.
Mix the cornstarch and water to create a slurry, then slowly whisk the slurry into the saucepan and cook for 2-3 minutes until the glaze thickens slightly.
Pour half of the glaze over the ham, letting it seep into the slices, and reserve the remaining glaze for later.
Cover and cook on low for 3-4 hours, basting the ham every hour with the juices in the slow cooker.
About 15 minutes before serving, transfer the ham carefully to a serving dish.
Reheat the reserved glaze if needed and brush it generously over the ham, ensuring it's well coated.
Broil the ham in the oven for 2-3 minutes for a shiny, caramelized finish, watching closely to avoid burning.