Stir the flour to aerate it. Dip your measuring cup(1 cup) into the flour, without shaking the cup overfill it. Aerating the flour and not shaking the cup are the keys to the right measurement.
Sweep the excess flour off the top with a spatula or with the back of a knife.
That's all! When you use a scale it should show 140 grams.
Notes
It will be easy to dip your cup into the flour if you keep your flour in a big jar.