Cut the sides away from the pit: First, cut a thin slice off the bottom (stem side) so the mango can stand upright without wobbling. Using a sharp knife, start at the top of the mango and cut off one of the wide sides, guiding the knife around the oval-shaped pit in the center. Repeat on the other wide side. (You will have two mango “cheeks”.) Cut away the short sides the same way.
Score the mango: Place the mango skin-side down on a cutting board. Cut a grid through the mango flesh by applying enough pressure to cut down to the skin but not right through it. (A smaller paring knife may be easier for you to use for this step.)
Cut the mango flesh away from the skin: Push the skin inside out so you have cubes of fresh mango sticking out. Cut the diced mango away from the skin with a knife or scoop it out with a spoon.
You can also trim any extra mango flesh from the pit to make sure there is no waste.
Notes
A ripe but still slightly firm mango is easiest to cut. If the flesh is very soft and the skin is wrinkled, you can still cut the mango, but exercise more caution. The mango will be a bit harder to handle since the flesh is so soft. The flesh may also not hold in sturdy chunks and can easily fall apart or turn mushy.
Refrigerate the diced mango in an airtight container. It is best used within 24 hours.