Preheat oven to 400 degrees F (200 degrees C). Place ham on a rack set in a roasting pan, and carefully pour about 1/2 inch of boiling water into the pan beneath the ham.
Bake the ham in the preheated oven for 2 hours, or until a meat thermometer inserted into the thickest part of the meat (do not touch the bone) reads at least 140 degrees F (60 degrees C.)
Reduce oven heat to 350 degrees F (175 degrees C.) In a bowl, mix together the brown sugar, flour, dry mustard, honey, and lemon juice as needed to make a thick, smooth paste. Brush the ham generously with glaze. Skewer 1 pineapple chunk and 1 maraschino cherry per toothpick, and insert the decorated picks all over the ham.
Return the ham to the oven, and roast for 15 minutes. Baste the ham, fruit and all, with glaze and juices that have collected in the bottom of the pan, return to the oven, and roast for an additional 15 minutes. Let the ham rest for at least 10 minutes before slicing.