This happy hat is a modern riff on the classic crocheted granny square. Subscribe to KnitBits for a weekly newsletter with free patterns!
The panels are joined with a stem stitch, which is an embroidery stitch. Here is how to do this stitch.
For instructions on how to make a child sized version of this hat, see this blog post: http://stitch-story.blogspot.com/2011/10/make-childs-vers...