Use blanched almonds (according to these instructions) and put them in a grinder/food processor. I've found that the blanched almonds to almond flour ratio is just under 1.5:1 i.e. 1.5 cups of almonds will make just under 1 Cup of almond flour.
Pulse the almonds for 10-15 seconds at a time. In between pulses, shake up the blender to make sure the nuts are close to the blade again, then continue to pulse and pause/shake until the flour is ready. *
Sieve the powder to collect any larger bits which you can then blend/grind again.
Transfer into an air-tight jar/container. You can store this in the fridge for 1 month or the freezer for 3 months.
* It should have a fine powdery consistency when ready. Make sure to watch the blender closely as you do the pulses - the oils in the almonds will heat up and loosen while blending, so you run the risk of getting almond butter if you pulse for too long. You've gone too far if the nuts begin to clump on the sides of the blender jug.Note* You can also use a coffee grinder to create the almond flour. However, this method is more time consuming as you'll need to create the flour in small batches, due to the size of the machine. It can also flavor your flour slightly if you use the grinder often for coffee. If using a coffee grinder then you can sieve the almond flour, then re-blend any of the larger pieces for a second time, into a fine powder.