Over the years, I have expriemented with various layerings; granite , maple, MDF , marble & thin lead ,etc.
The most significant challenge for me dealt with the discovery that certian reflections / vibration returned from the platforms affecting whatever electronics that sat on that platform. Not that all colorations sounded bad to my ears , but distortation is the muck of audio-swampland.
I found the coupling either dry , bolted , glued and/or the compound used in gluing had and equal impact . Thus, the whole sheebang and the apparent random-ness of what sounded "good vs bad " started to drive me "audio-insane (AI)" , until, I bought the resonance dampers The Stillpoints.
The Stillpoints sit beneath my unsuspended turntable that sits above a 4hx15wX18d" custom-made platform of seasoned mapleblock. No AI anymore -- just music.
The motto of my story : A platform is just a platform for troubles until its isolated from the electronics above.