This exercise is taken from the regular two-legged RDL.
Start with two dumbbells, one in each hand. Stand on your right leg, keeping it slightly bent throughout the exercise. Reach back with your hips, keeping most of your bodyweight on your heel. Keep your back flat and let your left leg raise up as you lower yourself down. This will help you to maintain balance. Raise yourself back to the top by pulling with your hamstring and squeezing your glute at the top.
Repeat for desired number of reps on your right leg before switching to your left.