Start by naming any country that France borders. Then name any country that borders any of those countries. Then keep going until there are no more countries left to name.
Thank you for your comment! Those do end in "s", but are not single-name countries. My concern was that some multi-name countries' formal names end in "s", but their common/map name does not. For example, Saint Vincent and the Grenadines ends in "s", but it is more commonly known (on JetPunk) as just "Saint Vincent". The only exception I made was for The Bahamas, which does formally include "The" in its name.