As a practitioner of chaos magick, I wanted to share that while some of these symbols are commonly used in alchemy, they can also be used as sigils in modern practice. To create a sigil, it is necessary to encircle the intended meaning of the spell you wish to cast. I hope this information is helpful to you. If you need more informations about magick or looking for do something new in this context, I’m willing to help. :)
I don't mean to be "that guy", but there is no such thing as "necessary" within chaos magick. One of its core principles is the avoidance of dogma, and another is that reality is totally subjective based on belief. So sure, you can believe you HAVE to encircle the intended meaning or whatever, but that's not taught as a rule anywhere within chaos magick whatsoever.