This step is the most important: The webs.
Draw a rectangle from the supporting foot of your graphic up to the centre line. This height from the supporting foot to the centre line is important as it defines how far the graphic elements are pushed forward from the card. You can any length for the rectangles. In the case of the fir tree graphic, the width should be small, as the web is placed at the top of the tree, however it must have a minimum width of 2.5mm, so that the web does not bend.
As our design includes three trees, each with different distances, we need to create a separate web with the associated height for each tree. The webs are shown in the screen shot with a red filling so you can easily spot them.