1. Remove ham from the packaging.
2. Pour the pineapple juice in bottom of a large (6.5- to 8-quart), oval slow cooker.
3. In a medium bowl, mix the brown sugar, Dijon, balsamic vinegar, and honey into a paste. Spread brown sugar mixture all over ham and place, flat side down, in slow cooker.
4. Cover slow cooker with lid and set to low. Cook ham for 4 to 6 hours or until the meat is tender and the internal temperature reaches 140°F. If desired, flip and baste the ham halfway through cooking time and again about an hour before ham is done.
5. Once ham is done, remove to a platter and tent with foil to keep warm. Skim any fat and strain the juices from the crock pot into a saucepan. Place the pot on the stove over medium heat and bring the juices to a simmer. 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. 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. Do not add straight cornstarch to the hot liquid or it will clump, and do not over stir the sauce once the cornstarch has been added or it may not thicken properly.
6. Serve the ham warm, with the sauce on the side or drizzled on top. If you prefer an oven-cooked ham effect, you may also glaze the entire ham with thickened sauce and pop it under the broiler for about 5 minutes (watch it closely!) before serving.