01
Build the graduation schedule first
List slate lengths, widths, thickness ranges, course counts and exposures from eave to ridge. The schedule should fit the actual rafter length and preserve required laps through every transition.
02
Sort thickness with the visual hierarchy
Thicker pieces generally begin low on the roof, where they create a substantial eave. Abrupt thickness changes can lift upper courses, so transitions should be gradual and checked in a mockup.
03
Order for the real geometry
Each size covers a different area and produces different cut waste. Turrets, valleys and dormers complicate the schedule. Quantities should be calculated by zone rather than applying one average count to the whole roof.