Once you have the header, content and footer for the Panel as separate pictures, the next point is to set the cutting points for each element. The purpose of this step is to cut as separate pictures the (rounded) corners and a slice of the container background that will be either repeated either streched to match the height of the elements or fit the content.
In this step you should set the markers to cut as individual pictures the (rounded) corners, margins and a slice of the background. These design elements will be embedded in the CSS and used later to create the DIV based panel layout.

Slicing markers
You should try to cut the corners, margins and background slices as small as possible to get the maximum space for the Panel Content. The slicing should be reapeated for all the Panel elements - header, content, footer -