This is a really good question, and helps me realize how far I've come. Small talk used to be a nightmare for me, and now I work in customer support/training/coaching on a one to one basis.
I start off with getting the client comfortable in the room, by asking them how they are, how's their week going. I will also offer them a hot or cold drink. Although it is completely uninteresting for me, I'll mention about the weather or anything else that is topical, just to get the conversation going.
As I see them once a week, I make a point of remembering things they say, so I can follow up next week - not sure if that's small talk but it seems to work as it makes them feel like they belong. Some things that seem important I might write down so I remember to ask them about later.
Years ago, I would be the only one getting on with the job (completely different position), when my colleagues were standing around chatting together, and that made me feel miserable although I didn't know how to change that, which I've since learnt.
Are you able to observe other staff there for ideas?
I guess some occupational therapy assistants will come across as more efficient and 'getting on with the job', and others will come across as maybe more friendly and chatty. Where do you see yourself or would like to see yourself?