To prepare, line a 9x9 pan with parchment paper.
To a large mixing bowl, add your rice krispies, oats, walnuts and flax seed.
To a microwave safe bowl, add your peanut butter and honey. Stir them together till they are entirely combined. Microwave in 20-30 second increments, stirring in between, till the mixture is hot. Add your vanilla, salt and cinnamon to the hot peanut butter honey mixture and stir till combined.
Pour your wet ingredients over your dry ingredients and stir till everything is well incorporated, and your dry ingredients are covered entirely by your wet ingredients.
Pour the mixture into your pan and press it down using a spatula into an even layer across your pan, with a smooth top.
Place in the fridge and let harden for at least one hour.
Remove from the pan, cut into 12 or 16 bars, and enjoy!
*Store these bars in your fridge and they will last about a week.