Place rack in the Instant Pot and place corned beef on top of the rack.
Pour the water into the pot.
Add the garlic cloves, bay leaves, mustard seeds, allspice, salt and pepper to the top of the beef.
Seal the Instant Pot lid and the valve.
Cook on high pressure for 90 minutes.
Do a quick release and release all the pressure before opening the lip.
Take out the corned beef and wrap in tinfoil and set aside.
Add the bay leaf and garlic cloves back to the juice if needed (off the top of the beef).
Place potatoes, cabbage, and carrots into the pot.
Shut the lid and seal.
Cook for 5 minutes on high pressure.
Do a quick release and open the lid.
Serve immediately with the corned beef.