Abbie Slouch has a simple lace stitch pattern repeat. More repeats can easily be added for a slouchier hat if required.

The pattern contains a youtube link to the K1 long stitch which the pattern uses.

It has instructions for knitting in the round and flat.

Knitted in the round
1 x 2.75mm 40cm circular needle.
1 x 3.50mm 40cm circular needle.
1 set of 3.50mm double pointed needles.
1 stitch marker.
Wool needle for sewing up.
Knitted flat
1 pair 2.75mm knitting needles.
1 pair 3.50mm knitting needles.
Wool needle for sewing up.