This ear flap hat is super simple. Because the ear flaps are knit onto DPNs before casting on in the round, and knit right onto the cast on row, the flaps are seamless. While I chose to use garter stitch, the method is such that you could easily substitute almost any stitch pattern, and it would be simple to use other aran weight yarns with similar gauge to create stripes, stranded work, or whatever suits you.
I was able to achieve an 18” circumference because I have two sets of Addi circulars. Since the total circumference is created by the length of the cord and the needles, I use the cord with the shorter needles that give me that 18”. But this pattern would work on 20” circulars, DPNs or magic loop.
The 18” circumference of the hat easily fits a person with a 21” or 22” head, and a larger or smaller size could be achieved by adding or subtracting stitches, and using the technique given in the pattern.