Can I install my engineered wood flooring as a floating floor with underlay, over our floorboards?

Softwood floorboards usually require some preparation. First securely fix any loose boards. Then use a hole punch to punch down any nail heads. Check the evenness of the floor with a spirit level. Then securely fix 6 or 12 mm WBP ply over the floorboards. Then check the eveness of the ply surface. Any low spots can be made even by applying a fibre reinforced flexible feather edge levelling compound. Then install the underlay and engineered hardwood flooring.