To make a woman's size hat cast on 112 stitches of worsted weight yarn (I used one ball of Manos Del Uruguay) on a 40-47 inch long circular needle in US size 5. Push all of the stitches to the middle of the long cord of the needle and divide the stitches in half. Pull the cord out. There should now be 56 stitches on each needle. Here is a video showing you how to start magic loop.
Knit the hat in double rib (2 knit stitches and 2 purl stitches) until it measures 6 1/2 inches for a women's size hat (add another inch for a man's size hat). At this point start shaping the corn of the hat. Knit two together (K2tog) and purl two together (P2tog) for one round. Then knit one round in one by one rib (one knit and one purl). Next round K2tog all around and repeat this last round until 14 stiches remain. Cut the yarn leaving an 8" long tail . Thread the tail through the needle and pull through all of the remaining stitches. Pull down through the top of the hat and knot on the inside. Weave the ends into the hat.