The 'creativity' or out-of-the-box level of the case has no impact on the timing to structure or communicate. It should still be done within the same time frame as any other business question.
There is only a difference between McKinsey and Bain/ BCG:
At the core, McKinsey wants to see creative ideas communicated in a structured manner, the more exhaustive the better.
Your goal should be to come up with a tailored and creative answer that fits the question. The framework should - broadly speaking - follow these three characteristics:
You would need to go into detail and qualify your answer with practical examples and more details.
To come up with the framework you have 1-2 minutes (2 minutes is kind of a soft limit). Then, in a McKinsey interview, you can take up to 5-8 minutes to present your structure, your qualification, and hypotheses. This is due to the interviewer-led format that McK employs. The interviewer will only ask 'what else' if you
- haven't gone broad or deep enough
- did not explain your ideas well enough for them to stand out (again, you have time here)
The firm wants to see exhaustive and creative approaches to specific problems, which more often than not do not fit into the classic case interview frameworks that were en vogue 10 years ago...
Again, this only applies if everything you say
- adds value to the problem analysis
- is MECE
- is well qualified
- includes a detailed discussion of your hypotheses at the end
Summing up the core differences to Bain and BCG:
- You have more time to think about it
- You have more time to lead the interviewer through your structure
- You need to go wide and deep to create an exhaustive and creative structure, whereas in BCG/Bain you rather need to be focused and quickly zero in on the key points where the problem of the case is most likely buried
- Questions tend to be more creative and not suitable for classic frameworks, especially on the lower levels of the framework
- Instead of drilling through your framework, in the end, to look for answers to solve the case, in a McKinsey-style, you need to discuss what part of your framework you would want to prioritize
The difference in format and way of answering a question is the reason why I recommend preparing very differently for McK interviews vs. other consultancies.
Let me know if you have more questions!