Put oven rack in middle position and preheat oven to 325°F.
Sprinkle ribs evenly with salt.
Bring orange juice, soy sauce, sugar, ginger, garlic, and pepper to a boil in roasting pan over moderately high heat, stirring until sugar is dissolved.
Add ribs in 1 layer using tongs, turning to coat, and cover pan tightly with foil.
Braise ribs in oven until very tender, about 2 hours. (If making ahead, see cooks' note, below.)
Reduce oven temperature to 200°F.
Transfer ribs to a baking dish, arranging them in 1 layer, and keep warm in oven.
Skim fat from cooking liquid if desired, then make glaze by boiling liquid, uncovered, stirring occasionally, until syrupy and reduced to about 3/4 cup, about 15 minutes.
Brush glaze generously on ribs.
Ribs can be braised 5 days ahead and cooled completely in cooking liquid, uncovered, then chilled, covering them once they are completely cold. To reheat, set roasting pan with ribs and cooking liquid over moderate heat, covered with foil. Simmer, covered, turning once, until they are heated through, about 15 minutes, then transfer ribs to a baking dish and keep warm. Make glaze as directed.
