Foot Exercises: Contrast bath---It is a form of treatment where a limb or the entire body is immersed in warm water followed by the immediate immersion of the limb or body in ice water. This procedure is repeated several times, alternating hot and cold. Note that the treatment should always end in the ice water, as heat will induce the body's inflammatory response, while cold helps to decrease inflammation. • Point your toes • Raise your heels • Squeeze your toes • Roll a ball. Sports Taping

There are few exercises which can help u with flat feet Also see the link between knee hip and ankle