This post exists because SE no longer has community advertising. I expect the post to be closed and removed, but I hope a bunch of people will see it first.
What is the Sandbox?
The Sandbox is a page in Worldbuilding Meta where people can test their questions before putting them on Main. The goal of the poster is to avoid question closure. The goal of you, potential participant, is to help people learn how to ask good questions.
Why should I help?
Stack Exchange's rules were originally designed for people like engineers and programmers who need help overcoming specific problems in ways where an objective best answer is important. Worldbuilding is the most creative stack in the SE universe — but all those rules still exist. Helping people understand how to work with the rules to make the most of their experience here is incredibly valuable.
How do I help?
Visit the Sandbox, scroll down to an "answer" (potential questions are "answers" to the Sandbox "question"), read it, then post comments about how to improve it or whether or not you think it's suitable. Pointing out rules and policies the OP should be aware of is valuable. The Sandbox is a place for guidance about how to ask questions, it is not a place to get answers to questions.
If everyone visited the Sandbox once a month to help review just one question, it would improve the sandbox by about four orders of magnitude.
Why did you post this?
The Sandbox is listed in the Help Center, but few people bother reading the Help Center pages and even fewer do so regularly. As a result, most users don't think about the Sandbox much.
Thanks for reading this!