Sit up straight in a chair.
Place your feet flat on the floor hip-distance apart.
Lift your heels up and then lower.
Lift your toes up and then lower.
Lift the inside of your feet up, rolling onto the outer edge of your feet, and then lower.
Lift the outside of your feet up, rolling onto the inner edge of your feet, and then lower.
Repeat.
Ensure your hips and knees stay in the same position.