This may need editing later, so if you find any mistakes or typos, please let me know. :)
Pattern is for a single colour hat. For colour changes, work the first row of the new yarn in knit only.
(As demonstrated here.)
Using size 9mm needles and any super bulky yarn, cast on 56 stitches.
Join work to knit in the round (I used the magic loop method throughout... demo here).
K2, P2 until work measures 8 inches/20cms, or longer/shorter depending on how you want the hat. The finshed hat will be 1.5 inches/3cm longer than whatever your work measures before you start the decrease.
Knit all knit stitches together and purl all purl stitches together. 28 stitches remain.
K1, P1 to marker.
In my work, this resulted in the first stitch in the next round being a purl stitch, so I purled two together to the marker. If your first stitch after the marker is knit, knit two together all the way around to the marker. 14 stitches remain.
P2tog to marker. 7 stitches remain. Cut yarn and finish hat by threading the cut yarn onto a tapestry needle, pick up the stitches while removing the needles and pull tight to close the loop. sew in ends. How to end a hat demonstration here.