Leenia, my mango-cutting technique is simpler than it sounds. With a sharp, thin, flexible knife (a boning knife works well), cut all the way around the mango, stem to pointy end and back again, on both sides of -- and ideally right next to -- the seed. That will yield two seed-free "cheeks" plus a center section that is largely seed.
Take each cheek, and score the mango flesh all the way down to (but not through) the skin in a cross-hatch pattern that's as small as you want to chop/dice your mango. (You might want to use a different knife for this process; one with a rounded tip will make it easier not to cut through the skin, OR your hand.) Now, just turn each half inside-out to make 2 cute li'l mango hedgehogs. You can then run your knife along the skin and cut off the mango spikes whole, or cut halfway down and then all the way down for smaller dice.
Finally, run your knife under the skin on the center section, and then carve whatever mango flesh can be gracefully separated from the seed. Chop or dice those bits too.
Note: there are a wealth of YouTube videos on how to do this. Watch one, but keep this in mind: All the ones I watched show a whopping big chef's knife cutting straight down, not even trying to cut close to the seed. I'm way too cheap for that: With a thin, flexible knife you can feel your way right along the edge of the seed -- the only way to go!