Pattern and video teaching the construction and details are available on CreativeBug here
Subscriptions are now $4.95 / month so it’s a great deal
You can download the PDF from the project page once you subscribe.

This seamless pullover is worked from the center outward on the front and back and then joined at the shoulders. You then continue to work in one piece. The sizes are customizable. You keep working until you’ve reached the body size you want, then complete the sleeves and lower body.