"It has a lot more actionable advice than this Slate article."
I enjoyed the talk, but I don't really see how actionable the advice is. Or, rather, I think it's either wrong or what he says is incomplete. As he sets things up creativity is unleashed in sessions where you have "open" mind and you do the more mundane work in sessions with "closed" mind.
This bifurcation, at least as he sets it up with (e.g., "set aside at least 1 1/2 hours for your open mind session"), doesn't really fit with how creativity gets expressed. In many endeavors -- e.g., music, acting, sports -- the opportunity for creativity comes about only because of huge amounts of practice, in which the endeavor is developed to a point where it becomes second nature. Then, when placed in a situation where you have to perform, creativity comes out. I can't see how this fits with the process of switching from open mind to closed mind, as Cleese describes it.
I also have problems when I think of how creativity comes out in process of writing, whether it's writing fiction, non-fiction, or software. This process of getting work done is much more fluid than Cleese describes. People don't brainstorm for ideas for an hour or two, then sit down to do the mundane work. The work gets done in sessions that are better described by the concept of "flow", where if you still want to use Cleese's concepts of "open mind" and "closed mind" then it is best said that you drift frequently perhaps imperceptibly between the two.
Cleese's characterization in the talk is much more like brainstorming, where you just ponder, daydream, think things up, for an hour or two to find a right "answer", then go to work with "closed mind" implementing your answer. That doesn't seem to me to be how creativity happens, at least not for wide variety of different "creative" endeavors. Creativity comes out when you're in the flow, getting work done in single long session that is not characterizable as an "open mind session" or "closed mind session".