Step 1: Sprinkle 1/4 cup of the brown sugar in the bottom of a 6-quart slow cooker.
Step 2: Place the ham, cut side down, in the slow cooker. Pour the pineapple *juice over the ham.
Step 3: In a small bowl, mix the brown sugar, ground mustard, allspice, and ginger.
Step 4-5: Rub the spice mixture over the ham. Close the slow cooker and cook on HIGH for 6 hours.
Step 6: Remove ham from the slow cooker and cover in pineapple slices and wrap in foil until you are ready to serve. If you like, reserve the juice from the slow cooker and cook down on the stove top and brush the glaze over the ham.
Notes
I used my Instant Pot as a slow cooker for this recipe. I did not cook my ham with the pineapple slices because my family does not like cooked pineapple. If your family likes cooked pineapple places the slices on before you start cooking.