I'd run a lead ad targeted towards people with similar job titles or at competing companies. Include relevant job information (title, salary range, etc), then promote the ad as "easy application" and require full name, email and phone. Once they apply, send an email requesting their resume or get them on the phone. I work for a digital ad agency (AdvertiseMint) that specializes in Facebook and Instagram ads, we could help you set these up if needed. - Brian

This really depends on the job and market you're targeting. Like the other poster said you can target job titles at competing companies. You can target interests related to the business as well. The ad is critical as you want to ensure its optimized for performance

Look at the major brands and what they use and do the opposite. You need to write your ad as if you are speaking to only one person at a time. That person is your idea candidate. Just pretend that you could say something like this, "Hey Bob Smith, this is the perfect job for you. Read this ad and I know you will agree." Of course you can't do this, but you can keep in mind that you are focusing on one not the many. Secondly, write out at least 20 reasons that this candidate would want the position and try to get at least the top 3 in your ad.
I hope this helps.
Best of luck,
Mike

Recruitment via Facebook is quite easy. Facebook is the platform where everyone spends the most time. More than a billion people log into Facebook every day. Your organic reach on Facebook is limited to friends of your employees. You need people who live near your office. It is highly unlikely that your current employees will relate to someone who is perfect for the job – and even if they are, that person could easily miss it in their news feed. Any great Facebook Ad needs great visuals. Facebook's ad targeting is mind-blowing. Demographics are another critical element of Facebook ad targeting. In addition, you can target your ads, so they show based on a Facebook user's employer, job title, industry, and office type. Interests are another important aspect of Facebook ad targeting. First off, check out the relevance score on this ad: a 7 out of 10. On Facebook, engagement is the key. The higher your engagement, the higher your rewards from Facebook. Therefore, you need to know exactly who you want to hire. Targeting your audience based on the demographics, interests, and behaviours that fit your open position will result in more relevant ads and higher engagement.
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath