This fitness video shows how to do stomach-flattening exercises at home. Our host, Kathy, Kaehler, informs us that the best exercise is a yoga-based exercise called the plank, because it focuses on your core. Your core is where your abs are. This exercise is best done on soft surfaces. Start out at 15 seconds, and build up to a minute or more. To do the plank, rest on your knees and 1 forearm, with your side facing the ground. Make sure your body is straight. If you want to make the exercise more challenging, rest on your feet instead of your knees.