Yeah, I've never really understood how you can "talk through your thought process" for a question like "Why is a man-hole cover round?" It seems like you'd either come up with a reason or you wouldn't be able to come up with anything at all.

Perhaps you can say things like "Well, let's see...you need to be able to pick the man-hole cover up out of it's hole, then put it down somewhere, then maybe move it, ..." but I really think these types of ramblings are just stalling for time rather than an actual English narration of what I believe is an inexplicable thought process that would go into coming up with an actual answer to such a question.