thanks for asking your question in our Consulting Q&A :)
I found some old Q&As that might be relevant for you.
Ben, one of our users, shares his experience and gives great tips:
[You] have roughly an hour to review material, then have give a 10-15 presentation, followed by 10-15 minutes of questions. [The] strategy is basically: 1) Read the executive summary, 2) Go through the exhibits / figures / charts, 3) See if you have answered the question / have a hypothesis and supporting info. If the answer to 3 is yes, then I'd start with your presentation then; once you have that in a skeleton form, then perhaps scan the text to see if there are details you'd want to include; if the answer to 3 is no or youre not sure, perhaps scan the text first (before starting presentation) to see if that answers it.
Regardless of how much material is, some things to remember:
1) State your big conclusion at the beginning
2) Make sure you answer all the questions posed [...]
3) Limit yourself to 3-4 slides. And make them simple. [...]
4) Don't be surprised if they stop you mid-presentation and throw some doubt or new information at you ; just like an actual case, they're going to want to see you think on your feet. If you need a second to consider that, ask for it. Good cop/bad cop routines are common too.
5) Confident and concise, just like any case.
6) Leave notes / sticky notes / highlight key figures, sections, and areas from the case. In some cases you may want to refer to it (usually answering a question after your presentation).
You can find the original Q&A here: Bain Written Case Prep
In another Q&A, some of our experts give hints:
Guennael (Ex-MBB, BCG/Bain/Experienced Hire specialist):
We are looking for the same qualities in the written case as in the verbal one. You should have 1 hour to prepare so there's a little more time, but obviously you must actually prepare slides for the presentation. It comes down to time management. For example, agree in advance you will allocate 5 minutes to figure out what's going on, 30 minutes to the actual case prep, another 5 to confirm the order of the slide (story line) and the remaining time to go into pure slide-development mode. Ultimately though, if you can crack a regular case, you should be able to crack the written one as well.
Meghan (Ex BCG):
[...] We're also looking for decent presentation skills and ability to answer questions or be open to feedback without getting too nervous or (on the other end of the spectrum) coming across as arrogant. So, practice a case interview by yourself start to finish [...], then present your slides aloud, to yourself! [...]
Nick (Ex McKinsey):
Verbal or non-written cases pressure tests 3 elements, your LISTENING, thinking and verbalization, typically in a 30 minute interview; however, the written cases test only 2 elements, your READING and thinking, in 45 minutes period followed by a separate verbalization evaluated afterwards. Hence, by design the written is much easier - you just have to practice the key elements that gives you the advantage to do well. [...]
You can find the original Q&A here: Best Preparation Method for Written Cases at Bain and BCG?
Hope this helps!
Best of luck for your interview!