Slice steak against the grain and add to a ziploc bag. Add cornstarch, salt and pepper. Toss until well-coated

Add oil and turn on saute setting. Add steak and sear until browned

Combine soy sauce, garlic, ginger, water, brown sugar, vinegar red pepper flakes and sesame oil in a bowl. Add sauce to instant pot

Cook on high pressure for 8 minutes, natural release for 10 minutes before quick releasing

Form cornstarch slurry by mixing 2 tbsp of cornstarch with 1/4 cup of water. Turn on saute setting and add slurry. Cook until thickened

Top with green onions and sesame seeds, and serve over rice.