Place 1 cup of the rolled oats into a food processor or blender.
Pulse the oats 5 to 7 times until they are a coarse powder consistency.
Transfer the pulsed oats to a large bowl and mix with the remaining 1 cup of whole rolled oats.
Add salt, ground flaxseed, brown sugar, and cinnamon to the oats and stir until thoroughly combined.
Store in an airtight container or divide into four separate jars.
To serve, combine 1/2 cup of the mix with 3/4 cup of boiling water or milk, stir, and let stand for 2 minutes.