A creative oasis needs boundaries people can respect
One way I make that room is to leave my office and sit outside under a tree or in a comfortable reading area at home. In Phoenix, the reading area wins during summer. The point was to step away from the place where I was always responding to something.
At work, that might mean closing a door, using a quiet room, or protecting time on a calendar. It also means resisting the temptation to check one more message. A different room does very little if the same interruptions follow you into it.
I find the combination of space and time helpful: a clear start, a clear finish, and an understanding that ordinary requests can wait. An emergency is an exception. If the building is on fire, I still want someone to tell me.
There is no required setting or guaranteed duration. Start with a boundary that is realistic enough to keep. Bring a question, a sketchbook, or an unresolved design problem. Let the session be useful without requiring a finished artifact at the end.
Confidence and humor make unfinished ideas easier to share
Cleese's emphasis on play stayed with me because an unfinished idea can be awkward to say aloud. Someone may see a problem with it immediately. That does not necessarily mean the idea has nothing to offer; it may need another angle or a connection we have not made yet.
For a team, I would make exploration explicit before the review begins. We still know the problem, the users, and the constraints. We are giving possibilities a chance to develop before ranking them. Questions such as "What else could this help us see?" keep the conversation moving without pretending every idea is equally useful.
Humor matters to me here too. Serious work can leave room for a laugh. The distinction I took from Cleese is between caring about the work and making every conversation solemn. Nobody needs to perform a comedy routine. People do need enough confidence to contribute something that is not polished yet.