I'll say firstly that it is technically against the JaGeX Code of conduct. Additionally, telling people to Google something or use any search engine to navigate to a non-JaGeX approved website is also against the rules. However, it is rarely reported and acted upon and, in general, all of the people here found out about the site in-game. So what I'll say is that it lands in the very, very grey area and more than likely not result in any serious form of punishment.
To be absolutely honest, if you want someone to join, being indirect about how to navigate here isn't the solution. If you want them to join, tell them how to find us (the usual "Google 'Slayer Nest' and select the first option" should suffice) and leave it at that.