Bind a Loop Band to the door with the Utility Strap at your face level and place the box around 2 meters away from the door.
Grabbing the band, which must be in light traction, climb on the step.
8 per each side (better not to alternate) x 3 sets.
Leaning with your knee forward or with your torso backwards by pulling too much the band.
Further information in this article.