Confused about hardiebacker 6mm on plywood

[lukenn77]

I’m trying to get my head around the best way to secure 6mm hardiebacker to 18mm plywood subfloor. Plywood is directly on joists.

Hardie docs seem to mention both a non-flexible mortar and modified thin set.

I’ve got a bag of Keraquick and some bottles of LatexPlus waiting for collection from SF. Would this be suitable?
I’m curious what others have done?

 

[Tile Marble Granite]

Prime the plywood, apply adhesive then the 6mm Hardi-backer on top using the proper screws. Any adhesive would do the job.