Freelancing
Imagine that you are the founder of Playable - https://www.linkedin.com/company/playable-/ (No, they are not our client :)) and create a research-centric carousel post + LinkedIn caption on Playable ADs to show yourself as the subject matter expert.
The outcome is to get engagement and awareness about your company (Playable in this case) without seeming promotional.
Note: You will be judged on your research skills, topic ideas and social media writing skills (on precision and if it's upto the point) rather than design skills. Good design skills would just be a bonus but not a necessity :).