Begin by having your dog standing parallel to you on a non-slip surface.
Block the movement of one hind limb with your hand as you lure your dog forward to reach a treat. This should encourage some extension through the hip joint. Next, bring the food lure round to the OPPOSITE side, encouraging your dog to bring their head around to their opposite hip. This encourages a stretch through the lumbar spine.
Hold as far as your dog can reach. Your therapist should recommend hold duration, how many reps, and when this should be performed.