First step: Take the meat out of the refrigerator and allow to come close to room temperature. 5 minutes. It's ok for the meat to have a slight chill when going into the Instant Pot.Salt the Sirloin Flap. Use enough to cover the entire piece of meat. I suggest using Himalayan SaltThen using a brush, paint on some oil like canola oil. This will help the seasoning stick. Add the bbq dry rub. Add enough to cover the entire piece of meat. Allowing the meat to sit awhile with the dry rub on will help flavor the meat more.
Add 1 ¼ cups of water to the Instant Pot alongside 3+ tablespoons of soy sauce.
Instant Pot Cook Settings
Using the pressure cooker setting "Meat/Stew", Under normal heat, & set timer for 20 to 25 minutes. 20 minutes for more medium rare
The Instant Pot will pressurize fairly quickly and the timer will start to count down.
Once the timer goes off, allow the vent valve to release the pressure. Quick release. You do not want to slow release or risk overcooking the meat. After the Instant Pot lid is off. ( Safe to open the lid once the metal pressure indicator fails back into the Instant Pot -
Next paint of a nice coat of Teriyaki sauce. Do this quickly as the meat starts to rest a minimum of 5 minutes before slicing the Teriyaki sauce will soak into the meat adding great depth of flavor.
KEY: After resting the meat, slice "against" the grain for maximum tenderness.