The hat was knit on 16" US 11 circular needles holding two strands of Bartlettyarn (which is worsted weight/heavy worsted weight) together throughout. You could use a bulky yarn.
Cast on 64 stitches and knit in K2, P2 ribbing for 3 inches.
Knit one round plain, increasing 5 stitches evenly.
Knit plain (knit every stitch in every round) until you are ten inches (or a little more) from cast on edge.
K4, knit 2 together around.
K3, knit 2 together around.
K2, knit 2 together around.
K1, knit 2 together around.
Knit 2 together around. If necessary, continue this final decreasing until you have only 6-8 stitches left on needle. Break yarn leaving plenty of tail to go through stitches, pull tightly and secure. Finally, weave in ends.
This is a very sturdy and somewhat slouchy hat. If you want it slouchier, use softer yarn, perhaps some which is already bulky weight. I carried one color throughout, adding new colors as I ran out of the previous color. A pretty quick knit, but next time I will use metal needles instead of bamboo as the bamboo did what they do best, stick to the yarn do it does not slip off needles!
Since I rather like this hat myself, I may be wearing it out in the cold soon!