I've realized lately how important this is to my happiness and satisfaction with work. As a web developer though, I find I'm spending more and more time plumbing things together in a stop-start fashion and it's getting harder to achieve.
The best experiences I can remember were when I was building games prototypes in XNA. I was only using the basics of the framework and writing a lot of the engine myself. These days I'm using Unity which is great but once again harder to get into the flow state for me.
I'm feeling the temptation to go back to doing more things the old fashioned way just for this reason.
What type of work do you do that regularly gets you in this state?