This knot design can be used as a stopper knot, which prevents a cord or thread from unwinding or slipping off a ring or a loop... Here we're making it for its decorative qualities.
The strand goes towards the right first of all, then heads left, passing over itself, before turning right to come back underneath itself.
This action is the basis of this knot design.
Now all you have to do is to repeat this action three or four times.
Bring the strand back up to the top, passing through each one of the right-hand bights as you go: over, under, over, under... That's the knotting finished. To create the definitive version, take hold of the strand you began with and gradually pull tight.
Of course, there's nothing to stop you from making this knot longer by repeating the knot-tying actions as often as you wish.