In a medium saucepan, combine brown sugar, sage, cinnamon, salt, mustard, and apple juice.
Bring up to a boil, and then reduce to a simmer and simmer uncovered until reduced by about one third, 5-8 minutes.
Place ham in a roasting pan. Brush glaze over ham, being sure to get it in between the layers of ham.
Bake for about 1 hour and 40 minutes, or until ham is warmed through and darkened on top (about 10 minutes per pound). Glaze ham every 30-45 minutes, being sure the ham is not drying out. Cover with foil, if necessary.
Finish ham with a final brush of glaze and let rest 10 minutes before slicing and serving.