To lose the flab, you'll need to lose fat all over. There's no spot reducing. This will require a sensible
resistance training program, a good nutrition plan, and sensible
cardio exercise.
For strengthening the abs, I prefer doing compound exercises (deadlifts and squats hit the abs hard) and letting them get stronger along with all the other muscles. But you can try some of the exercises bodyshop suggested too. Just understand that no amount of abdominal work is going to get rid of fat on your belly.