The key to losing your fat is predominantly in your DIET . You can exercise your abs all you like, but if your diet is not manipulated for it, or your energy expenditure is not enough to cover the calories you are eating you won't lose fat. Article link for fat loss: Invalid Link Removed.
Plus, you can't spot reduce fat through exercise.
As to what body composition you are to see your abs, that will change from individual to individual, as sex, height, muscle mass, and genetics all come into play here.
As far as doing abs at home to build them up, there are plenty of things that you can do. Just select a few exercises (i.e. crunches, weighted crunches, double-leg raises, v-sits, deadbugs, etc.) and do them. Otherwise, make sure that you are doing core exercises in your resistance training sessions.
~Rosie
Team APPNUT