From the Knit Picks Website:

This knit-two, slip-two slip-stitch pattern looks difficult, but is really quite easy and goes fast. The seams-on-the-outside at shoulders and armholes make a neat detail. The pattern stitch is one you?ll use again and again for its fabric look or for a decorative border detail.

The boxy shape makes easy assembly and a comfortable fit. The shoulders are joined with three-needle bind off with the seam on the outside. The sleeves are added to the arm edges of the body in the same way.

Check It Out! has fun detail and is easier to do than it appears.