1. Place a rack in lowest part of oven and heat to 300 degrees. Remove glaze packet and all plastic from ham (including plastic disc covering bone) and discard.
2. Place ham, cut side down, in oven bag and transfer to a roasting pan. Add 1/4 cup pineapple juice and 1 teaspoon allspice to bag, then tie shut. Using a paring knife, make several 1/2" slits near top. Bake until center of ham registers 140 degrees, 1 hour 45 minutes to 2 hours 15 minutes.
3. Meanwhile, bring remaining 1/2 cup pineapple juice, remaining 1 teaspoon allspice, the brown sugar, rum, mustard, and red pepper flakes to a boil in a small saucepan over medium-high, whisking occasionally. Reduce heat to medium-low and simmer gently, whisking often, until mixture is syrupy and has reduced to roughly 1 cup, about 15 minutes. Remove from heat, cover, and set aside.
4. When ham reaches 140 degrees, remove roasting pan from oven and increase heat to 400 degrees. Carefully lift ham from bag and return to roasting pan; discard bag and cooking liquid. Brush one-third of glaze onto ham and bake 5 minutes. Brush on another one-third of glaze, then rotate pan and bake 5 more minutes. Brush remaining glaze onto ham and bake until glossy and caramelized, 5 to 10 more minutes.
5. Cover ham loosely with foil and let rest at least 10 minutes and up to 1 hour before serving. To carve, cut around bone to loosen spiral slices. Place slices on a serving platter along with meat remaining on the bone. Drizzle with roasting liquid, if desired, and serve warm.
Source: Hannaford fresh Magazine, March-April 2022