This is a great exercise to assist us in keeping proper posture when hip hinging or deadlifting.
I personally use it to warm up hip flexion.
Skip to the 6:25 mark here for a video demonstration.
Move slowly through this drill and keep all three points of contact throughout the entire motion. As you become more advanced you can increase the speed, which will prep the hamstrings for eccentric loads within your program.
Keep the dowel in contact with the back of the head, midback, and between the glutes.
Keep pressure into the heels, or better yet, utilize "tripod" foot contact
Increase speed to prep the posterior chain for eccentric loading.