There are many ways you could write a job advert, but, absent something pre-existing to work from, here’s the skeleton template I use.
This was written as part of wider documentation about ensuring healthy and inclusive hiring practices, so isn’t a self-contained fully-fleshed-out thesis, but it’s been handy for me to use and re-use.
The examples are a little contrived and brief, but should serve as a basic indicator of the kind of content intended.