I’m not sure that felt will withstand the compression under an object that heavy, it may soon stretch itself out to paper thickness, since it has no structural strength. Foams have the same problem. If you just want to prevent contact of the metals, I would think a thick mylar would do the job; cut a circle to fit the pot and lay it on the base.
If you want more space between them, maybe roll a thick unbleached cotton (sailcloth, osnaburg, canvas, etc) to the thickness you want and stitch it in shape as a pad (s). It will have more cohesion, being woven, and you’ll know the fiber content.