Stir pineapple with juice, sugar, vinegar, soy sauce, curry powder, ginger, and red pepper flakes into slow cooker. Season pork chops with salt and pepper and nestle into slower cooker. Cover and cook until pork is tender, 6-8 hours on low or 3 to 5 hours on high.
Transfer pork chops to serving platter, tent loosely with aluminum foil, and let rest for 10 minutes. Let braising liquid settle for 5 minutes, then remove far from surface using large spoon.
Whisk water and cornstarch together in a bowl. Transfer braising liquid to saucepan, add cornstarch mixture, and simmer until reduced to 2 cups, about 12 minutes. Stir in scallions and season with salt and pepper to taste. Spoon 1 cup sauce over chops and serve with remaining sauce.