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!
If your ham is too tall to place the lid on top of your slow cooker, simply cover your slow cooker with foil, securing it as tightly as possible. If possible, you may place the lid on top of the foil.
Internal temperature should register 140-145 degrees F.
Cooking time is will vary depending on the type of ham (bone-in or boneless), the size of the ham, etc. It's best to read the temperature of your ham using a digital meat thermometer.
Check the label- make sure your ham hasn't been artificially pumped with water or juices. The label on your ham should just read “ham” ... not Ham, water added or Ham with natural juices.