Usually you will get to interview two managers, one HR and one senior consultant. It involves one or two problem solving skills such as design a mobile checkout. As long as you justify your design decisions you should be good.

4 interviews + assignement + focus is a lot on years of experience due to nature of consulting. There are usually few managers including HR interview and decide as a group on candidates. Be prepared when you come to this interview and presentation of your work is extremely important.