I believe you will find that most frum lawyers end up working for small firms, as solo practitioners (which is a small firm with only one partner), or for the government.
While “Big law” is open to frum Jews, it is hard to land a job there (one needs excellent credentials and it helps to have the right social credentials and by definition if you are frum you don’t have the right social credentials). One should note that it appears that “Big law” (the large corporate law firms such as “Dewey Ballantine” a.k.a. “Dewey LeBoeuf”) are having problems, and one might suggest that planning a career in the hope of working for “big law” may be dubious choice.