Abs are tough as we know, but the way to really build those muscles (the fat is another story) is through strength training. Here is a great strength idea for those abs: the Jack Knife. There are two modification options to the regular jack knife you can try.
Option 1: Single-legged jack knife
Straightening your legs forces your upper body to reach higher in this exercise and works your abs more. If you cannot lift your torso as high off the mat, bend your knee and just reach as far as you can. Squeeze as you lift and as you lower. And remember to control the movement as you lower so you are not just falling to the mat!
Option 2: Jack knife with an exercise ball
This can be tougher because both legs are coming up at the same time and you are squeezing with your legs. Try not to drop your legs all the way to the mat.
Cheers Eights & Weights!