Rinse corned beef well. Reserve seasoning packet.
Cut onion into quarters and put in the Instant Pot. Put bay leaves in the Instant Pot. Put the trivet in the Instant pot on top of onions. Put corned beef in instant pot fat side up. Pour beef broth over corned beef.
Add seasoning pack to the top of Corned Beef.
Put the lid on top of the Instant Pot and close valve
Pressure cook corned beef 75 to 90 minutes and do a 15 minute Natural Pressure Release
If cooking a corned beef bigger than 3 pounds and closer to 4 pounds do 90 minutes. Add 10 minutes of pressure cook time for every pound over 3 pounds is a good rule of thumb.
Once pressure is released remove corned beef from the Instant pot.
Cut cabbage into six wedges and add to instant pot with carrots and potatoes. Put the lid back onto Instant Pot close valve and pressure cook vegetables for 3 minutes. When cooking time is complete do an instant pressure release.
Cut the fat off of the top of corned beef. Turn corned beef over so the fat side is down and slice the corned beef against the grain into 1/4 to 1/2 inch slices and serve.