Triceps kickbacks (or extensions) can be done in numerous angles, but one of the best positions for this move is from a quadruped (all fours) posture. Why? It encourages good form by allowing you to keep your back flat and supported during the arm extension so you get a lot more benefit (from challenge to support) from a single move.
To do it, start kneeling with a dumbbell (or end of an anchored resistance band) in one hand. Bend elbow up by side of the rib cage, keeping arm close to the body. Without moving the upper arm, straighten the elbow, reaching weight toward your hip. Return to bent position to complete one rep. Avoid swinging the weight and try to keep elbow in the same position (close to the side of the body) during the entire exercise. Try up to 3 sets of 15 reps on both sides.