Rather than scooping the almond flour directly with a measuring cup, spoon it into the measuring cup so that it's loosely packed.
The original recipe calls for castor sugar, which is more commonly used in the UK. You can certainly use granulated sugar as is, but I suggest pulsing it in a blender or food processor for 15 seconds or so to achieve a finer texture.
Recipe From:
It's Not Complicated | Gluten-Free Almond Cookies