To make a puff, cut a circle that is twice the desired size. The outer edge of the circle can be left raw-edged or can be finished off by any number of sewing (or serging) stitches.
Make a secure knot at one end of your thread and hand stitch an inner circle. I like to use a quilting weight thread so it is less likely to break as I draw up the stitches.
Next step: Draw up those stitches, gathering the fabric into a puff. Pull the gathering thread to the wrong side and knot.
Yes, it's as easy as that.
Here I've used free-form circles to make flower shaped puffs. Three puffs grouped together created a fast and easy corsage.