I'll be showing you how to make a separate trim, but you can always work this straight on to your project. (And when I'v egot round to finishing the cushion I want to put some on, I'll show you!)
To make your pompom edging you will need:
A suitable sized hook
i. start with a chain 3
ii. then chain another 3
ii. yarn over and insert into 3rd chain from hook
iii. now you're going to do the first half of a treble/double crochet so pull through, yarn over and draw through first loop on hook only.
iv. Repeat this twice more so you have four loops on your hook
v. yarn over and pull through all loops on hook
vi. slip stitch to secure.
vii. Now you're going to repeat the above steps into the top of the puff you've just made, so chain 3
viii. yarn over insert into the loop at the base of the chain, draw up a loop, yarn over and pull through the first loop only. Repeat until you have four loops on your hook.
ix. Yarn over and pull through all four loops, slip stitch to secure.
x. Now insert your hook into the very first loop from step ii. yarn over, and pull through.
xi. Now you're ready for the next one!