In a medium bowl, combine Spice Mixture ingredients and rub over trimmed brisket. Place brisket in a large ziplock bag or other tightly covered container and refrigerate 8 hours or overnight.
Pour one cup of water in the Instant Pot and insert the steam rack. Stack the brisket pieces on the rack, fat side up.
Secure the lid, making sure the vent is closed.
Using the display panel select the MANUAL or PRESSURE COOK function*. Use the +/- keys and program the Instant Pot for 75 minutes.
When the time is up, let the pressure naturally release for 15 minutes, then quick-release the remaining pressure.
Carefully remove the meat from the pot to a foil-covered baking sheet and brush with BBQ sauce.
Set the brisket under the broiler for 4-5 minutes until caramelized and bubbly.
Slice meat against the grain and serve.
Notes
*The MANUAL and PRESSURE COOK buttons are interchangeable.