I’ve done this to keep rolls warm:
Wet and wring out a small kitchen towel and put it in the bottom of the crockpot. Construct a kind of “trivet” of aluminum foil to put over that. I just roughly crinkle up the foil a bit and ensure that it’s a rough fit around the circumference of the pot and that it’s structurally rigid enough to support a little weight.
Keep the crockpot on low and pile your sliders on top of the foil and leave the lid ajar so it doesn’t get too steamy and damp inside.