my design consultant is still in bed, so: Fusion 360 - if I want to create a load of holes in a flat 2d shape, do I need to extrude it first, then create another sketch on that face and extrude the holes back?
That would work, you could also have them in the first sketch. You could also have points in the first sketch and then create holes using the hole function. None of them is the best option per se, they all give the same result but some respond better to various types of design changes than others.
my design consultant is still in bed, so: Fusion 360 - if I want to create a load of holes in a flat 2d shape, do I need to extrude it first, then create another sketch on that face and extrude the holes back?