What the best way to do site planning on a large wooded lot?
I would start with the county map of parcels and then get a Google maps aerial view.

Take those as PDFs and annotate them with your specified dimensions. Showing the driveways and building lots clearly overlayed on the county parcel map and aerial view.

You could also drive T-posts at specific points (surveyor's posts if you can find them) for the contractor to reference while working. GPS might not help since consumer level GPS is only accurate to within 5-10 feet. Not very accurate when locating a surveyor's post.

Lastly, be there on the day(s) they are working to verify they are doing what you want.

Good luck on your project!