If you have undefined waist, small hips, and no curves at all, we have the perfect solution for you.
What you basically need to do is define your waistline and add volume to your lower half. So here are some great designs that will look good on you.
Peplum Dresses and Skirts: They are perfect for adding volume for your straight and slim figure.
Belts: Add all sorts of belts to define your waist.
Define your waistline with different fabrics at the waistline.