Not every space is a box. A unit's shape can be a rectangle, a sloped top, tapered sides or a skeiling, and the cutting list gives you the angles to cut.
Step by step
Open the unit's size
Pick the unit and open Size and position. The Shape buttons are at the end of it.
Choose the shape
Sloped top: the top falls from one side to the other, as under stairs. Tapered: the sides lean in or out. Skeiling: the top falls from the front to the back, under a sloping ceiling.
Type its heights
Each shape asks only for its own sizes: the height at each side, or the height at the back.
Or let the ceiling decide
Where the room has a sloping ceiling, press Fit under the ceiling and the unit takes the shape of the ceiling over it.
On the cutting list
Sides, tops and shelves are ordinary boards with their ends cut at an angle, and the angle is written on the cutting list. Backs and doors are cut to shape, and laid out on the sheet by the rectangle they're cut from.
Skeilings
A skeiling (also skeeling) is the sloping part of an attic ceiling. A skeiling unit can open at its front or at one end, and its top can slope part of the way and then run level, for a cupboard that goes up to the flat ceiling. Its drawers get shallower going up: each takes the longest of your runners that fits under the slope.
Inside a shaped unit
Shelves, dividers and drawers go in spaces as in any unit, cut to the shape where they meet the slope. Shelf where the slope starts puts a shelf level with the low side, so everything above it is the sloped part.
Questions
Can a sloped or tapered unit have drawers?
Yes, in its spaces: the fronts are cut to the shape and each box is as big as fits. Drawers across the whole front, and worktops, are for rectangular units.
What if the unit goes up through the sloping ceiling?
It's flagged in the unit's problems and in Cutting & cost, and the unit's Fit under the ceiling button shapes it to the slope. Undo takes it back if you'd rather not.