By default, the display of Slate/detachable Chromebook is in landscape mode. One by Wacom tablet is also in landscape mode. They match with each other.
However, if you rotate your Slate/detachable Chromebook, you need to rotate One by Wacom along with it. That’s how Chrome OS is designed for Slate type of Chromebooks.
We do see some exceptions which portrait mode is set as default for slate/detachable Chromebook. So mapping results could vary depending on PC vendor's setting.