Do this
Cut lines about five millimetres apart at a shallow angle. Turn the piece ninety degrees. Cut the same lines again to make a grid.
Why it works
The cuts give heat a shortcut into the middle. They also give the surface somewhere to shrink, so the piece does not curl up at random.
When to skip it
Skip it for thin slices. The cuts go all the way through and the piece falls apart in the pan.
