Line an 8-inch square pan with parchment paper.

Add the oats to a large bowl.

Combine the butter, brown sugar, and honey in a saucepan over medium heat. Cook, stirring frequently, until the butter melts and the mixture comes to a boil.

Reduce the heat slightly and boil for 2 minutes, stirring frequently.

Remove from the heat and stir in the vanilla, salt, and cinnamon.

Pour the hot honey mixture over the oats and stir until thoroughly coated.

Transfer to the prepared pan and press very firmly into an even layer.

Let cool for about 30 minutes, then refrigerate until completely set. Cut into bars.