Flabby bellies are due to lack of muscle use. Sitting around letting your stomach slob over your belt or walking around that way is never going to help tone those muscles. Flabby abs is lazy stomach muscles. :)
From what I understand we can do all the sit ups, crunches, or tummy exercises we want, unless we dump fat it is not going to do anything but give us a bigger belly. Stomach fat accumulates because of the way we eat or don't eat. It is the storehouse for our bodies during the starvation periods. Problem is we never experience it, at least not all of us.
Change how you eat, hold in your stomach using both the lower and upper abdomen muscles and experiment with different exercise programs. Everyone has their favorite you need to find yours.
Me? I have a soft belly and am alright with it. :)