How do I get an interview at off campus firms?

Hey everyone, my school is a target (on campus recruiting) for some consulting firms including all of MBB, Deloitte S&O, etc. but has no on-campus recruiting for some major T2 firms (e.g. EY Parthenon, Strategy&, LEK, ATK).

I'm a junior looking to apply to summer roles and am interested in some of those firms -- how do I get my application read/realistically get an interview? If the answer is networking, how much is enough to get an interview? If i have a couple decent calls with junior consultants there, is that enough? Do I need a referral from someone more senior? Or should I make some kind of explicit ask? I'm confused about the logistics and whether there's any way to be confident I'll get my resume read/have a chance for interviews.