AngelList has recently introduced a "sourcing" function. To source on AngelList, you need to define your company and post a job. Then, press the menu item "Recruit" to launch the Sourcing function:

The free search filters AngelList offers for Sourcing include keywords, role, location, looking for full/part-time, work authorization, years of experience, and skills. Many members have their resumes and social profile URLs attached to their profiles.

Additionally, AngelList would search for candidates based on your job description:

It's worth using for sourcing, check out the new functions!