There are three of the most popular and time-tested variants. The first one is freelancing sites, like Upwork or Fiverr. The advantage of such platforms is that they have a plethora of users that you can sort out by several parameters. In addition, there you can also post your job advertisement to freelancers.
‍
The second one is portfolio sites, like Behance or Dribbble. Their main benefit is that they allow you to assess designers based on their creativity and skills. They also provide you with an easy way of communicating with candidates.
‍
The third one is design subscription services, like Awesomic. For a fixed monthly payment, they take on all the hiring responsibilities, allowing you to focus on other more priorities. In the end, you get the top-notch logo designer without any stress.
Moreover, unlike the other variants, this one gives you much more than just a logo. After paying once, you are free to request dozens of tasks during the whole month. That means you could develop more brand elements, including brand books and even corporate templates like email or presentations.