As a 'seasoned adult', I've had many years of experience in areas of not-for-profit, as well as paid employment.
Having trained several incoming staff through a variety of various positions, I noted it can be difficult to pass on all information that the incoming staff member may require.
Trivial things such as where floral arrangements/wreaths are purchased, or what to remember at various times of the year may not be recorded in the job guidelines but are intrinsically part of the role.
That's where a "How To" document might be helpful. In this document (which I refer to as a 'living document), you note small incidentals, timelines, and practical notes that can assist the incoming staff member as they learn about what is required, especially after you are no longer working in that area. Looking back, I now realize that such a document in my early years of working in both paid and N-F-P work, would have been invaluable.
This document can be continually changed and updated by those referring to it so that as functions, timelines, and things change in your role, there is an up-to-date place of reference. It is an intentional document and one you are continually updating.
Such a document might seem to be a waste of your time, however, once you are not in that role, it can assist the new person, especially if they cannot contact you. Such a document, alongside the PD and PG, can stimulate conversation and help with communication in the working environment.
One way you might like to begin your "How To" document is by going through your Position Description (PD)/Guidelines (PG) and making notes on the small points that are not listed in these documents.
In some roles, knowing the manager's coffee preference can help set a more positive start to the working day!
Small incidental points, which seem trivial, can help create a positive working environment, or cause dysfunction as people become frustrated because the previous staff member "knew", but the new member of the team does not.
How can you create a "How To" document today and into the future, for when you train someone in your role?