This video shows you a quick way to create a sloping top for your Polyboard model, either from left to right, or from front to back.
To take the example of a cabinet in a loft, you would typically measure the wall up to the slope roofing.
Then decide how far out you want the unit to be in depth and take a plumb line to measure the height of the front of the cabinet.
The difference between those 2 heights is the figure you enter in the ‘Depth Slope’ parameters box.