Ch - chain
Rnd - round
Dc - double crochet
Sc - single crochet
St - stitch
Sl st - slip stitch
Fpdc - front post double crochet
Bpdc - back post double crochet
Hook size: H (5mm)
Here is a tutorial I found on Youtube:
Rnd 1 - Start with a chainless foundation. You can read about how to make a chainless foundation in this tutorial. It makes the base nice and stretchy, which will be necessary as you are working this hat from the bottom up. Ch 3, then make a chainless foundation of 38 dc stitches. Join first st to last st to create a round.
Rnd 2 - Ch 2, fpdc, bpdc all the way around, sl st to first st. (This creates a ribbed stitching like you would traditionally see on the bottom of a hat or cuff of a sweater.)
Rnds 3-11 - Ch 2, dc around, sl st to close.
Finishing off the top of the hat - Flip the hat inside out, then sc both sides together to close. Alternatively, you could just sew it together. Finish off.
Create pompoms and sew them to the corners. Here is a good tutorial on how to make large pompoms. You're done!
To adjust this for bigger sizes, a.) crochet the chainless foundation until it stretches around the hat-wearer's head and b.) add double crochet rows until the hat is long enough.