You may need to process in batches depending on how large your blender or coffee grinder is. Blend on high for two to three minutes until a flour-like consistency forms. It's ok to still have large pieces as we will sift these out.
Over a bowl, sift the flour using a fine mesh strainer to remove the large pieces. You can reprocess these for another two to three minutes and sift again. You can also use a coffee or spice grinder on these large pieces to grind them even further but you may still need to resift.
Store in an airtight container for up to 8 weeks in a cool dry place. For longer storage, keep in a refrigerator.