Fill the stockpot with about 2/3 of water. Remove the stockpot from the stovetop after you bring it to boil. 

Cut the corned beef into thick slices. This process makes the meat reheat evenly. 

Put the corned beef slices into a cooking bag. Squeeze out as much air as possible and seal the bag using a plastic twist tie.

Immerse the bag into the boiled water. Make sure the meat is completely under the surface. 

Cover the stockpot and heat the corned beef for 10-15 minutes. 

Remove the bag from the hot water. Get the reheated corned beef slices from the bag. 

Serve and enjoy!