Chunky yarn + size 8 needles = fast and easy hat.
Start with a 4-stitch I-cord and make it long enough to tie a little knot in it. Then transfer them onto 4 double points (or two circs) and increase every stitch so that there are 4 stitches on each DP. These represent 8 sections of 2 stitches each.
Make sure to work a knit row every other round.
On the increase rounds, increase at the beginning of each of the 8 sections until there are 13 stitches in each section. Increase more for a more slouchy hat and fewer stitches for a less slouchy.
Knit even in stockinette until the hat is as large as you want it.
On next round, decrease once every 5 stitches (or as many as it takes for band to fit snugly). Work in K2/P2 ribbing for 2-3 inches if you want a single band or 4-5 inches if you want to turn up the band.
Do a stretchy bind off and BAM you have a hat.