Stand in front of a sturdy elevated surface, such as a Plyo Box .
Place one foot on the box and push on it to lift yourself up, without using help from the lower leg.
Come back down with control and switch leg.
Form tips
It is very easy to use help from the lower leg without realizing that you are. Focus on shifting your weight to the upper leg before pushing from it, and do not use any force in your lower leg.