How to make cookies without using greaseproof paper or a baking tin?
You should use what you have available as long as it is flat. Thin is good, if you have no cookie sheets you could use any thin-bottomed pans you have (thick bottoms take too long to get up to temperature, leading to inconsistent results). A layer of tin foil will work in lieu of greaseproof paper in most cases, shiny side towards the cookie.