Lock your feet in a hamstring machine, behind the bars or with some heavy weight put on them. Keep your hips extended and torso upright.
Keeping your hips extended, begin to lower yourself as slowly as possible until you can no longer control the descent.
At this point, allow yourself to fall to the floor in a controlled fashion and “catch” yourself with your arms.
Give yourself just enough of a push off the floor to get back into a position where you can pull yourself back to the start using your hamstrings.
Repeat for the desired number of repetitions.