Definition: Sl st is the crochet abbreviation for "slip stitch."
Learn How to Crochet a Slip Stitch
Examples: Ch 5, join with a sl st to form a ring -- This translates to "Chain 5, join with a slip stitch to form a ring." The picture shows an example of this. If you would like to see step-by-step instructions with more pictures, please visit my tutorial for how to form a ring in crochet.