To slice corned beef, rest the meat with its fatty side facing downwards for a few minutes. Note the grain of the meat, place a meat fork through its center, and cut thin slices against or across the grain using a carving knife.
Begin cutting the corned beef by laying it on a flat surface, such as a cutting board or a serving platter. Allowing the meat to rest with its fatty side facing downwards for approximately 10 minutes ensures that the internal meat juices distribute evenly through the roast.
The grain of the meat or the direction in which its muscle fibers run appears like shallow furrows that run across the length of the beef. Note this direction, and insert a meat or carving fork firmly through the beef's middle so that it remains in place.
Now, place the blade of a sharp carving, chef's or slicing knife perpendicular to the grain of the corned beef to cut the meat against or across its grain. Use a gentle hand movement when cutting. This ensures that the cut piece is not stringy and retains its shape.
Cut slices that have an approximate thickness of 1 inch. When slicing, begin at the lean end of the meat, and proceed to the fatty end.