Today we are looking at something called Puffy Couching, a method I found in A-Z of Embroidery Stitches 2.
Updated: French name: Couchure fantaisie "puffy"
You need either some thick woolen yarn or a hank of threads, folded in half and anchored down.
You then start couching with tight stitches.
Then lift up the hank of threads with the needle before you make the next couching stitch.
Continue until you have a bumpy line of couching.
You can vary the height and length of each bump, or keep them even.
This might be a challenge on the Aida, but do your best.