How to Crochet Puff Stitches
Crochet puff stitch is essentially the same as crochet bobble stitch. However, bobble stitch is worked using stitches that are double crochet or taller. Puff stitch is worked only using half double crochet stitches. Because of the unique third loop in hdc, it must be worked slightly differently than a regular bobble. Here are the instructions for a 5 hdc puff stitch:
Yarn over and insert the hook into the stitch where you are creating your puff stitch. Yarn over again and draw through. There will be three loops on the hook.
Repeat four more times. Each time adds 2 more loops to the hook. There will be 11 loops on the hook for a 5 hdc puff stitch.
Yarn over and pull through all loops on the hook.
Optional: Chain one. This step is used to secure the top of the puff stitch closed. It is rarely used so check your pattern instructions to see if it's required.
There are variations on this basic set of instructions for puff stitch. For example, some instructions will have you pull through some of the loops on the hook as you work, so that you don't have to pull through so many together at the end. One example is seen in the Puff Stitch Round Pillows pattern.
If you prefer illustrations to photographs, here are the instructions for a 3 half-double crochet puff stitch.
Yarn over, insert the hook in specified stitch, yarn over again and draw a loop through (three loops on hook). Repeat two more times, inserting the hook into the same stitch (seven loops on the hook); yarn over and pull yarn through all seven loops on the hook.
A cluster of half double crochet stitches is worked the same way as a puff stitch but each "leg" is worked where indicated.