Cut the parchment in two pieces along the crease. Place one of the pieces down into the baking pan, creasing in the corners so it sits in place. If it helps, rub a bit of butter on the bottom of the baking pan so that the parchment will stick and won’t slide around.
Also question is, how do you grease a cake pan without parchment paper?
Using a clean paper towel or pastry brush, distribute a thin layer of either: vegetable shortening, oil, or butter inside of your non-stick cake pan. Don’t grease all the way to the top of the pan. Grease only about 1 inch up the sides. No parchment paper required for this method.
Besides, how do you make brownies not stick to the pan without parchment paper? Using aluminum foil works nicely as well as a liner for the pan to get the brownies out in one piece. Cut a piece of foil so that it’s big enough to line the pan and also extend over the edges for about 2 inches. Press into the pan and butter or use baking spray.