Fusion 360 - Is it square is it round? (External Louvre)

From a FB question 0:00 Intro 4:50 Start design 7:58 Number of Louvres 13:32 Surface bodies 15:53 Extrude base body 16:28 Thicken surfaces 17:50 Chamfer 18:45 Fillet 19:50 Shell 23:25 Extrude plate to 3 mm