Before you actually start making the cake, turn on the oven (180-200 degrees) and prepare the tray.
I took a 24x34 cm glass tray (taken from Ikea, at a very reasonable price). You can use any other deep tray of about the same size.
You can spread it with baking paper or as I did - grease with butter and sprinkle well with breadcrumbs, so that you have a straighter edge to the cake (I noticed that the paper deforms a bit, that it does not fit well on the walls tavii).
If you don't have breadcrumbs you can grease the tray with butter / oil and spread paper, so it will stick better to the walls.