If you are looking for something free, but ad supported with regards to Flarum hosting, you can try out https://freeflarum.com. The pre-installed extensions that the site owner has provided should be more than enough for you to start your own community ?
Please also see the 3rd party Flarum hosting provider's discussion here for more information about the service he provides as well. You can ideally provide your own domain if need be if you don't mind using a subdomain name under lets say... example.freeflarum.com as your Flarum URL?
Flarum is FOSS (Free and Open Source Software) so ideally you can host it all on your own if you please.
