Also see https://aviationweek.com/aerospace/emerging-technologies/nasa-set-next-gen-airliner-wing-laminar-flow-flight-tests

Even if laminarity can be achieved, it is notoriously hard to sustain. “We plan to explore how off-design conditions affect laminar flow extents,” says Lewis Owens, CATNLF flow physics investigator at Langley. “How sensitive is this laminar flow shaping design to leading edge surface roughness changes? We created various 2D arrays of surface roughness elements to be temporarily applied to the wing leading edge to test the laminar flow sensitivity to increased surface roughness levels.