Wattpad - If you don't mind/don't know Wattpad, I see an awful lot of fanfics, some of which that... I think... Have gone so far as to being published. (: But they aren't bashed there. It's really popular, honestly. I love Wattpad, not only for its stories but for the community. I've known Wattpad for five years now and I think this is the number one place.
FanFiction - Fanfiction.net is another one. I personally don't prefer this one (I used to go on it) but I've heard a lot of good things about it. Perhaps it's because I don't really read/write fanfiction unless it's really good... (I've only ever read a handful and written two, which I enjoyed writing! I only read them upon request)
DeviantArt - I read a few decent fanfictions here (more like one lol), but I'm not sure if this would be for everyone... I don't recommend it, but it is a possibility, I suppose, especially if you draw as well! :P It's known for its artistic/drawing community, but I've seen both!
Quotev - I've looked around a bit, on my more intense story-writing days and stumbled upon Quotev, but I didn't stay. I've heard it's good, though, more recently. I checked it out a bit and it looks pretty good now! :3 It may be worth looking into.
These are the only ones that come to mind when I think "fanfiction". Most, if not all, fanfics I skimmed over on these sites had their own unique OC(s), so I'm sure you'll find it easy to slip into. Though my number one suggestion is Wattpad, any of these sites are great! It may be a little tough gaining recognition at first, especially if the site has a large and booming community such as Wattpad, (if that's what you want), but it will definitely come in time! You can always search "fanfic sites for [insert fandom here]" into a search engine if you want!
Good luck! ^-^
