Preheat the oven to 350 degrees F (180 degrees C).

Add the flour, butter, salt, and ground cinnamon to a food processor and pulse until it is combined and grainy in texture

Add in the maple syrup and water and pulse until it comes together to form a dough. It will seem dry and crumbly at first, but as you continue to pulse, it will come together into a dough. If your dough is extremely dry, add an extra tablespoon of water, but be careful not to add too much so that the dough is not sticky.

Split the dough in half and set one half aside. Place the first half on a lightly floured sheet of parchment paper and place another sheet of parchment paper on top of it

Use a rolling pin to roll out the dough between the two sheets of parchment paper to get it to be as thin as possible. The key to getting crunchy cereal pieces is to roll the dough out thin. The dough will slightly puff up while making, so roll it out as thin as you can. Slowly peel away and check to make sure that the dough is an even, thickness. I usually like to use a pizza slicer to shape the rolled dough into a rectangle to make it easier to get uniform pieces, but this is optional.

Brush a light layer of melted butter on top of the dough (Note: make sure the layer is light so that the cereal is not greasy when baked. You want a layer that is just enough so that the cinnamon sugar will stick)

Sprinkle a generous amount of cinnamon sugar all over the dough and lightly smooth it into the dough

Place the 2nd sheet of parchment paper back on top of the dough sheet and carefully flip it over. Gently peel back the parchment paper from that flipped side and repeat steps 5 and 6 with the melted butter and cinnamon sugar.

Use a pizza slicer or knife to slice the dough into squares that are ¼ inch to ½ inch in length. Transfer this sheet directly to a baking sheet (no need to separate the squares as they'll separate once they bake). Repeat steps for the remaining half of the dough and bake for 10 minutes, or until the edges are golden. They will be soft at first right out of the oven but will firm up as they cool.