Let me tell you right now, it's not!
It might be easier for me to say since my hair is naturally crazy / messy / what have you but I will do two different tutorials on how to get the same effect.
Sorry it's so small - still working out how to use gifs!
Steps for hair that's naturally crazy / messy / what have you
What you'll need : pony tail holder(1) Give your brush a break and start with your hair down and 'slept in'
(2) Pick up your hair as if you were going to put it into a normal pony tail
(3) Start looping your hair through the pony tail holder and stop half way creating a loop on the inside of the band and a tail on the outside
(4) Swing the 'tail' into the hand holding the loop
(5) Twist pony tail holder once and then secure around messy bun
Steps for hair that's naturally fine / delicate / what have you
Having hair that is naturally straight, fine, or flat, you can start off by:
(1) Washing your hair upside down
(a) This gives your hair volume!
(2) Blow dry your hair upside down
(a) Again, all about the volume.
(3) Add a sea salt spray like TGI's Love Peace & the Planet 'Totally Beachin' spray
(4) And blow dry your hair (you guessed it!) upside down. Try to scrunch the hair so it gets a really nice messy texture.
(5) By now it should be nice and full so go ahead and complete the above steps.
Hope that helped a bit - happy bunning!