Lovely hat in front/back post double crochet. The rib edging is double - it looks great and also gives extra protection for your ears in the cold. The hat is made top--down in one piece.
In the pattern you will find a photo tutorial for post double crochet.
The pattern has written instructions and a chart.
I have descirbed how to make 3 different sizes: Child - hat circumference 51 cm, small adult - hat circumference 54 cm, large adult - hat circumference 57 cm.
You will make the hat to measurement, so you don’t need to make a gauge swatch, but to get the right measurement you might need to adjust hook size.

Yarn: Tynd uld from Geilsk (288 m/50) - 2 skeins
Yarn alternative: Anina from Filcolana (210 m/50 g) - 3 skeins
Recommended hook: 3 mm

Pattern is available in english (US terms), german and danish.