Put a trivet in inner liner pot of your pot. Then add water or juice, liquid smoke, and Apple Cider Vinegar to the inner liner pot.
Prepare the Ribs
Lay out the rack of ribs with the meaty side down onto a baking sheet.
Remove thin membrane (also called silver skin, if it's still on there) by grasping it with your bare hands (or a paper towel) and pulling down the length of the rack.
Liberally sprinkle dry spice rub over the ribs and gently rub it in. Then flip the rack over and do the same to the other side.
Roll the rack into a "C" shape and put it in the pot sideways (meaty side will face the outside of the pot). You can also choose to cut the rack into a few pieces and stack it in the pot.
Put lid on the pot and close it, turning the venting knob to Sealing position.
Press Pressure Cook (Manual) button/dial, and then the +/- button/dial to choose 25 minutes.
The pot will take a few minutes to come to the pressure, and will begin the cook time when the pressure is reached. After cook time ends and unit beeps, it will enter the NPR, or Natural Pressure Release phase. The display time will begin counting up.
Let it NPR for approximately 10 minutes. Use a wood spoon or something to carefully turn the knob to the venting selection and release rest of the pressure until the pin in lid drops, which is indicating it is safe to open the lid.
Remove rack of ribs using tongs, then place on a baking sheet.
OPTIONAL: Turn your oven to BROIL at approximately 400° and set the oven rack approximately 8-10 inches from element.
Pour your BBQ sauce on hot ribs and use a brush to cover them.
Put pan under the broiler for a few minutes (until sauce gets bubbly). Do not leave the ribs in there too long as they might dry out.