Remove ham from the packaging and discard any flavoring packet that may come with the ham. If using a bone-in ham, check the end of the bone for a plastic cap; if present, discard.
Place the ham in the slow cooker. Sprinkle the brown sugar over the ham. If you have a spiral ham, make sure to lift the ham sections and get some sugar sprinkled in there too.
Pour the container (not drained) of Pineapple over the ham and brown sugar.
Cover slow cooker with lid and set to medium-high. Cook ham for 4 to 6 hours or until the meat is tender and the internal temperature reaches 140°F. If desired, baste the ham halfway through cooking time with the juices and again about an hour before ham is done.
Once ham is done, remove to a platter and tent with foil to keep warm.
In a sauce pan add 2-3 Cups of the pan juices. Place the pan on the stove over medium heat and bring the juices to a boil.
In a small bowl, use a fork to stir the cornstarch into the water to make a slurry. Slowly pour the slurry into the pot while whisking the ham juices. Whisking constantly as you add the slurry.
Allow the mixture to bubble and thicken for a minute or two, stirring occasionally. If you desire a thicker sauce, you may stir in a bit more cornstarch slurry.
While I previously mentioned, you could brush this glaze on the ham and bake it in the oven for a thick and sticky glaze on the ham. However, it is just as easy to ladle some of this delicious sauce over the ham and enjoy. I also put some in a gravy boat for those that want even more of this delicious saucy flavor for their Holiday ham.