i'm glad you're considering this!! so are you looking for examples of like how they look/work when active, or examples of how to set one up? i'm going to assume the latter, but if you wanted examples of functional ones too let me know!

https://efiction.org is what i use, and what most old-school fanfic archives ran on (if they used anything at all besides just straight html, anyway). it's extremely easy to set up as long as you have a domain with php. it kinda lags behind in updates, but it's still very much usable!

https://getourchive.io/ is newer and way more advanced. you need vps and need to be okay with python... which i do not have and am not. i'm waiting for a release with an installer that does it for me lol. but it's one to keep an eye on!

wordpress (a self-hosted domain) is also a decent option, and there are plugins and themes that make it look more like a publishing archive.

i think some other fanfic websites use different CMS but i am not all that familiar with them.

what i'd really love is seeing a newer, easy-install software for archives, but i don't know if it'll happen. but i can hope!