The first question that comes to mind for me is that if you ever wanted to replace that cloth- would it not be very difficult to completely remove it from the slate? Seems to me it would have to be scraped off where it was glued; if the glue is as strong at it appears. I would think that scraping glue and cloth off a slate would gouge the slates and make it uneven for the next cloth installation.
I am not an installer- so maybe I am totally wrong in my assumption- but anytime in my life that I glued a material to a flat surface - the material could never be removed without some unevenness left on the surface. Either, glue, material, or both had to scraped off the surface in some areas in order to apply new material evenly. Just think of replacing something like wall paper or old linoleum floors.