Seeking PhD students on traditional job sites
Sorry, but that thought makes me a bit itchy. Maybe I'm just old. 

Building up your reputation and visibility is a good thing, though. You might be able to do it with a university sponsored web site on which you have at least some control. Showcase your work and interests there. Publish links to papers if appropriate. 

It is also a place to say that you are "accepting PhD candidates". If you have funding available be sure to say that as well as what topics you would be interested in supervising. 

Another way to potentially find students is to attend conferences at which you are likely to find a good number of undergraduate (or MS level) instructors. Use the social contacts there to spread the word. You might possibly even get to meet a student or two. If you can get on the program, you also spread your reputation. These may be educational focused conferences, such as the SIGCSE conference of ACM in Computer Science. Most of the attendees there are educators and many are also supervising graduate students. 

But, maybe you are just a bit bored. If you have the possibility (and are at a large enough place) you can associate yourself with working groups of other professors on topics of mutual interest. It may be that the group itself attracts potential students and you might benefit from that as well as the synergy of joint work. 

I'm still thinking about your question and may add more as it occurs to me. I'd warn you, however, that with an advertisement you will likely draw a lot of responses that you will find entirely inappropriate and yet have to deal with. I'm thinking mostly of the ill-prepared who have little idea about what is required.