Unfortunately, there is no exercise that will flatten your stomach. Any exercise used to target your stomach will actually make it grow. Your abdominal muscles are much like the other muscles in your body—if you work them out, they will grow.
The way to flatten your stomach is through diet and cardiovascular workouts. This will remove the fat on top of your abdominal muscles and in turn flatten your stomach.
First, cut out as many simple carbohydrates in your diet as possible. For example, sodas, sugary drinks, candy, and other desert items.
Second, up your water intake. You can drop body fat percentage noticeably in a month with drinking a gallon of water a day and changing nothing else.
Third, run/jog your butt off! Or in this case your belly off.
I only do about 2 minutes of ab work a week and sometimes I don’t do it at all. Abs are made in the kitchen and treadmill!