Do you want your handfasting ceremony to be legally binding? If so there are forms to be obtained, filled in and returned to the Registrar’s Office which are your responsibility. You must:
Contact the Registrar in the district in which your wedding is to take place 4-6 weeks before the proposed date of the ceremony. This is to fill in a marriage notice form - to to send off the copy you have downleaded from their website. Failure to do this could lead to the postponement of the wedding. Allow more time if one of you has been previously married as the Registrar has to satisfy themselves that there is no legal impediment to the marriage.
The Registrar then prepares a marriage schedule which has to be collected in person by one of the parties to the marriage and given to the celebrant before the wedding can take place. It is a criminal offence under the Marriage (Scotland) Act of 1977 to solemnise a wedding until the relevant Marriage Schedule has been produced.
After the ceremony (which should be at the time, date and location outlined on the Schedule) the couple should then arrange for the Schedule to be returned to the Registrar within 3 days of the marriage taking place.
Your handfasting ceremony allows considerable scope for personalisation according to your wishes and spiritual beliefs but to be recognisable in law as being a legal marriage it must include:-
a declaration by the parties, in the presence of the celebrant and of two witnesses that they accept each other as husband and wife, and
a declaration by the celebrant, after the foregoing declaration, that the couple are now husband and wife.
You may wish to consult the National Records Office for Scotland's website for more information (and the downloadable forms).