Remove the packaging and discard it along with the plastic cap on the bone. Also, discard any flavor pack that may come with the ham.
Pat the precooked ham dry using a kitchen towel.
Add brown sugar, balsamic vinegar, Dijon mustard, and maple syrup in a medium-sized bowl. Mix well until it reaches the consistency of a paste.
Spread this paste generously over the pre-cooked ham.
In a large crockpot, pour in the pineapple juice.
Place the marinated precooked ham in the slow cooker. Make sure the flat side of the ham faces downwards.
Seal the slow cooker with a lid and set the temperature to low. Cook the ham for about 4 to 5 hours or until the internal temperature reaches around 140 degrees F and the meat is tender. Don't forget to baste and flip the meat at intervals.
Remove the fully cooked ham from the slow cooker and place it over a serving platter.
Cover it with tin foil and let it rest for 15 minutes.
Strain the leftover fat and juice from the slow cooker into a saucepan.
Place the saucepan over medium heat and bring it to a boil. Reduce the heat and let the juices simmer.
In a bowl, mix cornstarch with water and pour it into the juices. Stir and let it simmer until the mixture starts to thicken up.
Serve this gravy alongside the sliced ham, and enjoy!