Whisk together the King Arthur Gluten Free Measure for Measure Flour, granulated sugar, salt, ground cinnamon, and baking powder in a medium bowl.

In a small bowl, whisk together the egg, oil, honey, and 2 tablespoons of the milk. Add the wet ingredients to the dry ingredients and stir well until combined. If the dough is too dry, add an additional tablespoon of milk.

Use your hands to gently knead the dough together into a ball until the dough is smooth. Form the dough into a disk and wrap in wax paper or plastic wrap and chill for 1 hour or overnight.

When ready to bake, preheat the oven to 300 degrees.

Divide the chilled dough in half. Roll each half of the dough out on a piece of parchment paper. The rolled-out dough should measure approximately 14"x10" and be about 1/16" thick.

Carefully transfer each piece of rolled-out dough (still on the parchment paper) to a half-sheet baking pan. Use a sharp knife or pizza-cutter to cut each piece of dough into 3"x2" rectangles and trim the edges. Then prick each rectangle 2-3 times with a fork.

Bake the graham cracker sheets for 30 minutes, rotating the pans halfway through.

Once the graham crackers have baked, turn off the oven, and open the door for 5 minutes. After 5 minutes, close the oven door, keep the oven off, and let the graham crackers dry in the oven for 25-35 minutes. The graham crackers will continue to brown and crisp.

Remove the graham crackers from the oven and carefully break the crackers into pieces along the scored lines. This will give them that classic, jagged-edged look. Cool the graham crackers completely on a wire rack before storing them in an airtight container.