Lay the country style ribs out on a sheet pan.
In a small bowl mix together the brown sugar, kosher salt, black pepper, garlic powder, onion powder, smoked paprika (and optional cayenne pepper). Stir well until there are no large clumps remaining.
Sprinkle the salt & seasoning rub mixture on the ribs, coating both sides and pressing it in so it sticks.
Pour the water, Worcestershire, and cider vinegar into the Instant Pot. Crush the garlic cloves and pop them into the liquid in the pot.
Add the trivet to the bottom of the Instant Pot (the metal trivet that came with your pot). Place the seasoned boneless ribs on the trivet in the pot.
Put the lid on and lock it in place. Turn the pressure valve to seal. Set the Instant Pot to cook on high pressure Meat/Stew mode for 18 minutes. At the end of 18 minutes do a natural release of pressure for 5 minutes, then finish with a quick release. NOTE- While the pressure is releasing PREHEAT THE OVEN TO BROIL. Place the cooked ribs on a sheet pan and coat one side with desired amount of your favorite BBQ sauce. Broil in the oven for 4-5 minutes. Remove the ribs from the oven, flip them to the other side, coat with BBQ sauce. Place back in the oven for 3-4 minutes.
Enjoy your tender Instant Pot Boneless Country Style Ribs!!