Place one dumbbell on the floor. Position yourself with your toes on the ground and your hands on the bench as though you were doing a plank with the body straight and extended at 45 degrees. You may need to position your feet wider for support.
Push one hand in to the bench and row the dumbbell with the opposite hand by retracting the shoulder blade and bending the elbow, pulling it to your side.
Then lower the dumbbell to the floor and repeat for the opposite hand.