The bonded ceremony is more so of an announcement that two are bonded (which is almost physically noticeable for witches as they’re hyper sensitive to auras and so on). To actually bind yourself to someone can happen 3 different ways.
The Old fashioned way when a familiar and student are very connected and spend so much time together they ’accidentally’ bond. They can tell, however, that they’ve bonded by feeling an astral connection between them. Bonded’s auras also tend to overlap or mesh together and stretch between the space they’re apart (hence as to why telepathy works long distances with bonded).
2. The familiar and student consciously decide they want to be bonded and go to the headmistress who will bind them. However, binding does not always work as ”the old fashioned way” was how binding happens naturally. If two are not compatible in binding, their auras will reject each other and the process will be broken. (Just to make it lore friendly that witches or familiars dont choose their bonded. I think a lot of people will go the old fashioned way, though.)
3. The witch or familiar independently bind themselves together through an ancient, unknown spell shared between them. This usually occurs in souls of witches and familiars that have been bonded in past lives.
NOTE: When a witch and Familiar binds its not uncommon for the familiar or witch to see lights, the astral plains,have tingly body parts, or witness their auras melding together.
(If you are confused or have seen I have left something unclear, please contact me! 🙂 )