Hi there,
While I'm not familiar with Slalom specifically, I have the following advice:
1) Reach out to HR and simply ask directly. Ask if you should expect a case format or not
2) As an experience hire you're expected leverage your existing experience in your answers to a much larger extent. You will really have to talk like an expert and need to leverage your past experience to make the right recommendations
3. They will almost certainly align you to the vertical in which you have experience. So, if you are experienced in strat & ops, you'll work in strat & ops across many industries. If you're an industry hire, you'll work across a range of topics/services/functions for that industry.
Hope this helps and good luck!