Recipes might say to weigh the flour or at least scoop and scrape so the cup is level but it really doesn't need to be that precise. I don't even use measuring spoons for exact measurements of baking powder. I just scoop what looks like half a teaspoon using an actual teaspoon, not a measuring teaspoon.

Now if it says 500 grams of flour and you use 1kg, it's going to be a problem. But +/- 10% isn't noticable.