Pamir Style Mittens
Pamir mountaineers crochet their socks and mittens with slip stitch for many hundreds of years. Unlike most of crochet stitches, slip stitch technique produces elastic fabric like in knitting technique. Warmer apparel is another advantage comparing to any other crochet and even knitting stitches.
Crochet Slip Stitch is what crochet chain is made of. If continue working with slip stitch every other round, the fabric will look like in these pictures.
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Correction to the pattern:
Work in slip stitch in rounds inserting the hook through the front loop of each stitch.