Try either. I would say sleep for 5-6 hours and have an alarmclock. Thats what I do. Gradually I have programmed my self to wake up after 5-6 hours naturally.

It should come naturally eventually. In fact sometimes I just directly fall back asleep and I still have a ld. you could say I am a natural who has learned to be natural. hehe. I wouldn't say I am a natural. I have learned to make it more natural. 8)