Heat olive oil in a large skillet over medium heat. Add pork chops to the skillet and cook until browned, about 5 minutes per side. Transfer to a slow cooker and top pork chops with onion and green peppers.

Whisk tomato sauce, brown sugar, vinegar, Worcestershire sauce, and salt together in a bowl. Pour sauce into slow cooker, gently stirring to coat pork chops and vegetables.

Cook pork chops on Low until tender, 6 to 8 hours.

Transfer pork chops to a serving platter. Tent with aluminum foil to keep warm. Whisk cornstarch, if using, into sauce until thickened. Spoon sauce and vegetables over pork chops.