After a hard freeze the foilage dies so I cut it back and place the dormant clematis in an unheated insulated garage for the winter. Also put some shredded leaves on top. Nothing else is done to it until new growth starts in March/April when I pull the pot out and set it near a sunny garage window or put it outside.

I set the pot on something (wooden boards, lawn chair, etc.) to get it off the floor as have been told that the cold transfers from the cement floor to the roots and they can be damaged. No idea if that is true or not.