Go to
https://www.google.com/flights/#sear...018-01-25;sc=b
(I just gave you a dummy example so that (hopefully) you are using the older version)
Change the departure airport and duration to your specifications.
Further, click into the depart date field. A calendar picker should appear with two further options: Flexible Dates; Price Graph. If your dates and times are not set these two pickers are very useful.
Hainan and Air Canada are usually the two lowest fare airlines for Biz. Both lie flat on the long leg I believe.