A super simple and quick method to cut baking paper for a round tray, very useful when baking cakes. I saw this method in a show by Jamie Oliver, since then that's the only way I've cut it.
Here's a picture of everything you need - scissors, paper and a round baking tray.
Cut a piece of baking paper, measure it on top of the tray to be about the same size as its diameter.
Then fold the cut piece of paper in half.
Then fold in half again.
Then bend so that you join the corners of that square, as if you were making for a cornet.
And so bend the cornet until it becomes thinner, it would be about 2-3 more times.
Turn the tray upside down. Place the tip of the stream in the middle of the tray and cut the cornet with scissors exactly where the edge of the tray ends.
Here you can see what the cut cornet looks like and its position when you cut it.
Open the cornet and see that you get a round piece of baking paper, exactly according to the size of the tray.
Success!