This hat is roomy enough to fit comfortably over a small hair bun.
It has short row construction, that is worked sideways and knitted flat. It starts with a provisional CO, is knitted in wedges and ends by grafting the edges together. The first 14 stitches are worked in garter stitch which provides a ribbing - while the rest is knitted in stockinette.
Their are two versions of the pattern - one to the exact size and gauge as given below, and one more general version so that you can adapt it to your head size.