I supplied this "how to tie a sliding adjustable knot" information to my customers and have received lots of great feedback, so I'm offering it to you here too.
Here you can see a Bone Manaia and alongside it, the end of its cord, showing the sliding knots. These are great, cos you don't need a clasp and you can make the length of the cord just what you want, meaning you can wear the necklace different ways depending on the clothes you want to wear it with.
Step 1: Step 1
In the picture, the left hand (LH) cord is Pink and the right hand (RH) cord is Off-White. So imagine those are the two ends of your necklace cord.
Take the end of the LH cord and wrap it around the RH cord, looping it back to the left as pictured. Slide the end of the RH cord over to lie alongside the main part of the pink LH cord.