Set on the ground like you're actually in a hurdler. One stretched on in front of you and one behind you bent like it would be in an actual hurdler. Grab your foot in front of you and stretch as far as you can.
Stretch out those Hams and Hip Flexors!! Also, build muscle in the abs, quads, glutes, and lower back to lift those muscles. Flexibility is nothing if you don't have the strength to control it! :)