Bringing your best to an activity or performing extremely well. Used sometimes in contact sports where you are very physical and dominate.
After making a lot of big hits during a sport one would say "DANG! You were laying the lumber out there!" or after getting a very good score on a test you brag to your friends "Yea I just laid the lumber on every single question. That test had nothin on me." OR before an activity a coach might say to his team, "Get out there and LAY THE LUMBER!"