Op. 7 hat is a beautiful gift for children.
Op. 7 is a fun project for knitters who want to advance their knitting technique and go beyond knit and purl.
Op. 7 is also a get-it-done-in-a-day project which can be finished very soon.

Skills needed:
Knit
Purl
Make One
Slip stitch
Knit two together
These are all easy and useful skills.

And I just made a tutorial of SLIP STITCH:

Happy Knitting