Steve,
If the concrete floor of your basement is finished smooth, then you won't need any cardboard. The tops of the furniture sliders have a deep foam pad, so the legs of your table will "seat" right down in the foam, and the bottoms of the sliders are ultra smooth, so the table will glide along the floor.
Even if the floor isn't finished smooth, I think the sliders without carboard would be better. If you put cardboard under the sliders, the soft paper will crush down into the rough concrete and "catch" as you try to slide the table. This won't happen with the furniture sliders, as they are really hard and smooth on the bottom.
If you put the cardboard on top of the sliders, then the legs of the table will slip off of the gliders, because the bottoms of the legs won't seat down into the foam on top of the sliders.
Hope this helps.
Mannyrock
