Prepare the ham. Spray a large 6-7 quart slow cooker with nonstick cooking spray. Add the ham and sprinkle with brown sugar, covering the top and sides.
Prepare the glaze. Add the pineapple juice, marmalade, Dijon mustard, minced garlic, fresh rosemary, ginger, and black pepper to a small pot over medium heat, whisking well to combine. Bring to a low simmer, stirring often. Remove from heat and pour the mixture directly over the ham, separating the ham layers to help infuse the flavors.
Cook the ham. Cover and cook the ham for 4-5 hours on low, or until the internal temperature reaches 140 degrees F.
Reduce the glaze. Carefully remove the ham from the slow cooker to a large clean platter. Transfer the juices to a small sauce pot over medium-high heat. Simmer for 10 minutes or so, or until the liquid has reduced by approximately one-third.
Serve. Spoon the reserved glaze over the top of the ham and serve! Enjoy!