Hangover is a Baker boy cap knit completely in the round.
You start with the shield and cast-on the body stitches afterwards and connect them to the shield (this is the most tricky part). Afterwards you knit the ribbing, increase the stitches for the style of baggyness you prefer (the more stitches, the more baggylike it will get).
The shield needs no cardboard or anything to stay in shape.
You can see two versions in the pictures. The red and white one is knit with two strands of 4-ply sock yarn (one in red and one in white) and is the baggiest version. The blue version is knit in 4-ply cotton sock yarn only and in a less baggy style.
For the cotton version you need about 60 g of 4-ply sock yarn. For the red and white version you need 60 g of each colour of 4-ply sock yarn.