Gridding extremely lare datasets can be slow. In Surfer 15, grididng has been multithreaded so it proceeds much faster than in earlier versions.
The best way to grid large LiDAR data sets is to create a point cloud layer from the LAS/LAZ file and then use the Create Grid command on the Point Cloud ribbon page. Instructions on how to create a Point Cloud map ar ein this article: How can I view my LiDAR data?
This is much faster than gridding the LiDAR data set using the Grid Data command or the Map Wizard.
Updated November 11, 2017