Insert rack into the Instant Pot. Place piece of corned beef (can be rinsed) on top of rack. Add prepared onion, carrot, celery, and bay leaf. Add water for cooking. Other liquid options are above in the post.
Seal and cook on high pressure for either 90 minutes (sliceable) with a 20 minute natural pressure release, or 120 minutes (pull apart) with a full natural pressure release.
Remove meat from pressure cooker and remove to plate. Keep all the liquid and other items in the the pot, and add the prepared cabbage.
Seal the lid and cook for 10 minutes followed by a quick release. Serve immediately or store in an airtight container for up to one week.