Spray slow cooker with non-stick cooking spray.
Rub roast with 1/4 cup brown sugar. Place roast in crock pot.
In a bowl, mix together chicken broth, teriyaki sauce, remaining brown sugar, ginger, garlic, chili pepper flakes, black pepper and onion powder. Pour on top of roast. Cook on low for 6-7 hours OR high for 3-4 hours.
Remove roast from slow cooker and place on plate. Shred with two forks.
In a small bowl, mix together cornstarch and cold water, then add to the liquid that remains in the slow cooker. Let cook on high in the slow cooker for 5-10 minutes or until it starts to thicken (to speed up this process, you could pour the remaining liquid in a saucepan and heat on your stove top over high heat until the sauce thickens up). Pour sauce on top of shredded pork.
Serve over rice and with stir-fried vegetables.
To make this a freezer meal, rub roast with brown sugar and place roast in a gallon-sized resealable freezer bag. In a bowl, mix together chicken broth, teriyaki sauce, remaining brown sugar, ginger, garlic, chili pepper flakes, black pepper and onion powder. Pour on top of roast in bag. Seal bag and place in the freezer. When ready to eat, remove from freezer and place in fridge for 12-24 hours so that it can thaw. Pour contents of bag in slow cooker and follow the cooking and serving directions above.