Preheat oven to 300 degrees. In a large bowl, combine dry ingredients (oats, chopped walnuts, flax seeds, salt, brown sugar, and cinnamon)
In a saucepan over medium heat, brown butter. Stir occasionally, until you see light brown flecks start to form. This should take about 4-5 minutes.
Add vanilla, browned butter, and honey to the dry ingredients. Pour over top of the dry ingredients and stir until everything is evenly coated.
Place on a baking sheet flat and packed together (this will also help to encourage clumping).
Bake for 30 minutes, turning the granola with a spatula halfway through for even toasting. Be sure to check regularly, so as not to burn the granola.
Let granola cool completely before storing in an airtight container.
Notes
Resist the temptation to move the granola around once it comes out of the oven, just let it sit on the sheet pan. Let the room temperature air work its' magic. Don't mess around with it until it's hardened, or it won't clump!