I've never found slippers warm even the ones with wooly linings.My feet were cold today, despite woolen socks and comfy felt slippers with wool lining. Had to put a couple of those heat pads in them that are normally for painful shoulders and backs.
Is this a 'getting old' thing? I never used to get cold feet
Maybe try 2 pairs of socks..one thin and a thick woolen pair over them. And wear boots?