The base framework is in place. Standard L-girder, made from plywood dimensional lumber. Just about everything is salvage from previous layouts. Sitting on top is sheet cardboard – to provide a semi-solid base for track planning doodling.
I do not do the CAD track plan thing. I just don’t find it easy to sketch in those programs. So I will use track templates (turnouts, cross-overs, etc.) and some sweep-sticks for radius measurements. I can also use several building mock ups to help figure out how the urban scenery can work. Reaching over a wheat field is very different than reaching through an alley. You can’t really get a feel for that in a CAD design.