This is a four-step exercise that I usually do with a body bar and a "vertical" (facing the short end) step bench, but you could do it bare handed and get a lot of the benefit. The main thing to remember is that you MUST keep your spine in neutral, and do all the bending from your hips, NOT your waist.
beats 1,2) Standing about arm's length away from the bench, do the lowering phase of a stiff-legged deadlift, to either place the bar or your hands onto the bench
beat 3) step back with right leg
beat 4) step back with left leg to a plank position
beats 5,6) step in with right leg and do the raising phase of a one-legged stiff-legged deadlift
beats 7,8) step in with left leg, stabilize and prepare to repeat on the opposite leg
If one-legged standing is too challenging at first, you can modify by stepping in right on beat 5, stepping in left on beat 6, and rising on beats 7-8.
Speed comes from what you put behind you. - Judi Ketteler