Work with this topic is most productive when the theme can be given some time.

Because it is not traditional school mathematics it offers a good opportunity for students to explore something new and experience the emergence of structure for themselves.

Allow plenty of time for discussion :

How do we begin to talk about something which for most of us is just a tangle of string or a tied knot we do so automatically, like a shoe lace or a reef knot, that we hardly think about it ?

A knot collection might make a stimulating talking point for students in a classroom.