Preheat oven to 275 degrees F (135 degrees C). Line a baking sheet with aluminum foil.
Combine fennel seeds, black pepper, sugar, garlic salt, kosher salt, and cayenne pepper in a small bowl.
Place rib racks on the prepared baking sheet; cut several shallow slits in the membrane along the backs of the ribs with a sharp paring knife. Rub fennel seed mixture on both sides of ribs.
Bake in the preheated oven for 1 1/2 hours. Flip ribs and bake until a fork inserts easily between the bones, 1 to 1 1/2 hours. Set aside to cool completely, about 1 hour.
Combine brown sugar, orange juice, vinegar, orange zest, and hot chile paste in a saucepan over medium heat. Bring to a boil, reduce heat and simmer until reduced by half, about 5 minutes.
Increase oven temperature to 425 degrees F (220 degrees C) and line a baking sheet with aluminum foil.
Cut rib racks into individual ribs; toss with glaze in a large bowl until evenly coated.
Place ribs on the prepared baking sheet. Reserve any additional glaze in the bowl for basting.
Bake glazed ribs for 5 minutes. Flip, brush with remaining glaze, and bake until browned, 5 to 10 minutes.
