A sweet-and-spicy glaze offsets the richness of pork belly in this hearty dish. Pair with Cheddar-Chile Waffles, if desired.
In a small skillet over medium heat, toast chiles until charred and fragrant, 1 to 2 minutes. Remove chiles from skillet and set aside. Add cumin seeds to skillet and toast until fragrant, 1 to 2 minutes. Place chiles and cumin seeds in a spice grinder and finely grind. Transfer to a medium bowl along with black pepper, salt, and sugar. Remove two tablespoons of the spice mixture and set aside to make the glaze.
Rub remaining spice mixture all over pork belly. Cover and refrigerate for 6 to 8 hours.
In a small saucepan, combine reserved spice mixture, orange zest, 1/4 cup orange juice, cinnamon sticks, and maple syrup. Bring to a simmer over medium-low heat and cook until slightly thickened and heated through, about 5 minutes. Remove from heat and set glaze aside.
Preheat oven to 300 degrees. Remove pork belly from refrigerator and rinse off spice mixture; pat dry with paper towels. Add remaining 1 cup orange juice and chicken stock to a roasting pan. Place over medium-high heat and cook until liquid just comes to a simmer. Add pork, fat side up, to roasting pan. Transfer to oven and cook until meat is very tender and easily pierced with the tip of a sharp knife, 2 to 2 1/2 hours.
Increase oven temperature to 425 degrees. Cook pork belly until browned and crisp, 30 to 40 minutes more, basting with reserved glaze every 10 minutes.
Remove pork from roasting pan and transfer to a cutting board; let stand for 10 minutes before slicing into 1/2-by-3-inch pieces.