There are some fairly easy steps you can take that other, more-diverse organizations have taken. First, you have to get rid of your referral pipeline, because hiring people your employees already know is the opposite of diversity. Second, instead of recruiting from organizations you've already heard of, like Stanford where this person came from, you park a full-time recruiter at institutions with practical diversity, like Houston, Georgia, UNLV, CUNY. Finally, you go for diversity of thought, by hiring philosophers and carpenters instead of CS grads. I know for a fact that were I to hire into my AI Ethics department, the last person I would recruit would be a Stanford AI researcher. I'd go directly to the philosophy department.