Pat,
Flynn never did lay out his routing maps within a grid. However, if you overlaid his individual hole drawings on grids, they fit precisely. If you'll notice, the grid with the green drawings shows the line of play, that is always perfectly lined up with the orientation of the green in the large grid field.
Tim makes an excellent point about the use of grids to determine area and cost computations. Flynn was highly regarded for his ability to accurately predict the amount of money just about anything on the job would cost in terms of time, amount of materials and money. Some clients appreciated this aspect of his design and build model. The Rockefellers were notable fans of Flynn's ability to provide accurate estimates.
Spending a great deal of time on site and designing on paper and redesigning on paper with an experienced crew and foremen that understood how to translate 2D into 3D according to the designer's wishes was important. Of course outlines could easily be staked off the 2D drawings, but even his close relationship with his construction crews and accurate detailed drawings would not be able to define the finished product in 3D. The stakes would show the depth and height of features were necessary. Sometimes Flynn would describe the details of features with drawings, especially earlier in his career if we consider the sample of archival materials.
7th green at Town and Country (became Woodmont) near Washington, DC, 1921--NLE.