The most direct (other than drawing directly onto the carving material) is the pencil method.
Start with an image drawn or traced in pencil.
Place it image-side down on the carving block.
...and rub it with your finger, the side of a pencil or any smooth edged tool.
Peel back the paper slowly. If the image is lighter in places, lay it back down and rub some more.
This is the resulting image from the Pencil Transfer method.