Working in Tunisian crochet makes a curling fabric because the bulk of the stitch remains on the back of the fabric for a lot of Tunisian stitches. All the Tunisian designs I have done for Annie's and others, including the ones sold on my website, I have designed specifically to
alleviate this curling (unless the curling is a design element). Here are some tips to helping to alleviate the curling in projects in which you aren't using a pattern.
Please visit my blog post HERE for a list of tips to alleviate the curling.