Shed/Office Conversion Floor Prep: Hardie vs SLC

We're converting our shed into an office and are stuck on how to prep the floors. Currently the floors are plywood. The contractor that helped us with the exterior told us to lay vapor barrier then Hardie board before putting down the new LVP floors. However, there's a pretty significant slope in the floor currently that we'd like to address with self-leveling concrete.

Do we need both Hardie and SLC? If so, what's the best order of operations?