The difficulty of a knitted shell stitch afghan depends on how intricate the pattern is. The New Stitch a Day website offers a video tutorial on knitting the shell stitch. According to the web page, the shell stitch is an intermediate stitch and good for beginning lace knitters.
The knitted shell stitch is worked in twelve rows and then repeated until the desired length has been achieved. To complete the pattern, understanding of basic knit stitches such as purl, knit, yarn over and knit two together, are a prerequisite. It is also advised to knit a swatch in the shell stitch to achieve the proper gauge.