The template reverse proxies the machine URL plus the /torrents/ subpath to flood (the torrent client) listening on localhost and port 3000 on the same machine.

        redir /torrents /torrents/
        handle_path /torrents/* {
                reverse_proxy 127.0.0.1:3000 {
                        header_up Host 127.0.0.1:3000
                        header_up X-Forwarded-Host {hostport}
                }
        }