I finished the mock-up and finally got to mapping out doors and windows. The hardboard with the vertical lines is going to be a board and batten foundation. The HO scale version used horizontal scribed wood for the building and vertical scribed wood for the foundation.
I started cutting scribed wood for the building. Note - when cutting the end roof angles don't discard the cut offs. They are used later for the smaller office.
Next up is laying out and cutting spaces for doors and windows then bracing.