I have had a long freelance relationship developing for a company that works 9-5.

I usually start the day around when they do, and engage in back and forth communication throughout the day.

I often find it helpful to disengage around 1-2pm and either go outside, go the gym, or work on some other project, and I don't come back until after they have all gone home for the day. Then I get a few more hours of work in before dinner.

Those uninterrupted hours after 5 are usually the most productive.