Again, this is an option.
Freelancers are different from an agency in that you are dealing with an individual rather than a team of people. You are outsourcing the task for them to do for you.
One of challenges, however, is that not all the skills you need to do advertising exist in one freelance person. For example, a Freelancer who can create your ads ( a copywriter) is not necessarily skilled at knowing how to publish those on the social media platforms, and vice versa. So, you may need more than one freelancer to cover what you need to do Paid Social ads.
Again, you will need an additional budget to your media budget to pay for your freelancer’s fees. It is fairly common to find freelancers that will cost at least £2-300 per day, although there are also some very cheap remote options to be aware of.