Vinyl comfort onto concrete floor, What goes down first?

[pug205]

Son in law has a concrete kitchen floor. He wants to lay cushion floor. What should be put down first, hardboard, plywood? How should that be fixed please?

[aeromech3]

Just a word of caution from my experience, as I just fitted cushion vinyl in my bathroom (on top of smooth 9mm OSB3) anything sharp that falls from worktop which is more likely in the kitchen, could piece the foam backed vinyl surface.