I used 100g King Cole Riot Chunky and a 6mm hook.
Foundation row: Ch44.
Row 1: TR in the 4th ch from the hook. Ch 1.* Skip the next ch and tr twice in the next ch. Repeat from * to the end of your row.
Row 2: 3ch, Tr in between the first 2 stitches (v) on the row below, 2tr in between each V or set of 2 tr on row below until the end of your row.
Repeat Row 2 until measures ****
Make picot edging.
Next row: *Ch3, ss into first chain you make. Dc in next 2 sts. Rep from * to end of row. Fasten off.
Fold in half. Sew along the bottom and up the side of the cosy. Weave ribbon in and out of the v stitch to pull together at neck of hot water bottle.