Do the still and the clip of the dish need a clean background or the real table?

Yes, when the still and the clip have to share the real table. A clean background only if it hides the cut, and then it is used in both takes, not in one. Pick the table and do not change it between the clip and the still. In the sierra the still is on wood and the clip is on a grey background. Still and clip share the same table, whether the service one or a cloth if both use it.