Spray slow cooker with non-stick cooking spray. Remove the ham from the wrapper and discard glaze packet. Place inside prepared slow cooker.
Rub brown sugar, maple syrup, mustard, and balsamic vinegar all over the meat using your hands. Pour pineapple juice into the bottom of the slow cooker.
Cover tightly either with the lid or aluminum foil and cook on low 4 to 5 hours, basting twice, during the last hour. You can also flip the ham during the last hour if desired.
Remove from slow cooker and let set 10 minutes. Slice the meat off the bone and serve warm.
If the spiral ham you buy is too large for your slow cooker, don't worry. I used a 10 pound ham and it was too big for the lid of my slow cooker to fit. Just place 3 pieces of heavy-duty aluminum foil over the ham, covering tightly. You basically are steaming it with a tight seal.