The best designers either already have a job, or are doing the freelance thing. So I suggest that you start with identifying companies that you think have good design and start looking through linkedin for the designers that work there. Next, reach out for a coffee/drink and see how amenable they are to talking about design at your company. If it's the right fit, the designer will be excited and you can move on to a more formal interview process. If the designer is happy where they are, ask if they know anyone who might be interested.

My funnel looks like this: -reach out to about 50 designers -15 of them are open to coffee -1 of those 15 are open to an interview

Note about freelancers: they tend to like the lifestyle that freelance provides. I've had luck with hiring on freelancers as part time contractors that actually show up on site, then gradually convincing them to join up full time.