there are lots of ways of getting good abs. but for the abs it sounds like you want, the easiest way to achieve it is by having a low bf%. however, this really isnt such a good idea for boxing, for many many reasons!

and remember, your abs might look good, but it doesnt neccisarily mean your gonna be able to take a punch in them... in boxing conditioning and strength is more important than how they look! its all very well being able to dazzle your opponent with an 8 oack, but if he drops you waith a jab to the stomach it kinda ruins the effect