Unless you're very lucky, chances are you have some work you want to do and some work you have to do. Break each hour into 45-minute and 15-minute slots to do your creative assignments and get through your must-do work items.
Here's how it works: Start each hour with your creative task. At 45 minutes, switch focus to your to-do list and tackle one or two items. After spending 15 minutes on that, it's back to creative work. The time limit adds a sense of urgency, while the beginning of each hour is a rewarding creative assignment. This gives your creative muscles a rest by doing some mechanical work, which in turn often sparks creative thoughts.
This idea is similar to the 52 minutes of work and 17 minutes of break rule for productivity, but it's meant specifically for creative workers. You can try either approach and see which works for you.