If ya lot ever wanted to "create an character in this particular universe, had created concepts or ideas that dwell in this universe" but had no way to like.. Publish it like this wiki is doing? Well, if ya keen or just want to place that idea so others may read it, then Tensei Shitara Slime Datta Ken Fanon might be the site you're looking for! Due to the nature of this universe, and the age of the itself (and an dedicated group), it may seem underwhelming, though you "could create powerful characters like Rimuru Tempest, or make an character that grows as story progresses!
As for the appearance, imo it looks good (I believe if the fanon site looks like its official counterpart, then people may get more motivated in creating their OCs and publishing, as it feels like an actual thing so it gets authenticity that they're in deed publishing an OC in the fictional universe). I'm also trying to format the character template to look more stylish (kinda like this site's), though it's hard.
Nevertheless, just wanna create or stuff, join :D