taken from serious.eat, adapted for the rest of the world that is not the US and lacks eletric power-tools in the kitchen.

Ingredients

This is an american recipe, it will suck to be you if you went all-metric system apeshit a couple centuries ago. Cups for example have up to 6 ‘standard’ sizes, ranging from 284 to 180mL, now if you think cooking is like travelling through history please go die in a time paradox.

I’ve provided equivalences using the worldwide approved one-meaning-only-fuck-intelligent-design-lovers unit named milliliter and went for the more used conversions with 1cup=236.5882365 mL, 1 teaspoon=4.92925975 mL and 1 tablespoon=14.78676478125 mL. FML.

• 1 1/2 cups brown rice flour. That would be 354.88235475 mL, thank you.
• 1/2 cup cornstarch (maizena). About 118.29411825 mL.
• 1/3 cup dark brown sugar. Around 78.8627455 mL I’d say.
• 1 teaspoon baking powder. I gave you that one already.
• 1/2 teaspoon salt. 2.464629875 mL, stay with me.
• 5 tablespoons butter, cold. Yeah sure, I gave up here. Who the hell carves teaspoons out of butter? I looked at my standard sized teaspoon for a while and cut around 75g of butter, with a knife for god sake. And don’t even get me started with the ‘stick’
• 6 tablespoons milk. A big one here 88.7205886875 mL.
• 3 tablespoons honey. You might have to use your fingers, honey doesn’t like leaving the spoon it’s in. Use about 44.36029434375 mL.

cooking:

1. Preheat oven to 350°F. 176°C is good too, prevents rockets to crash I’ve heard.
2. Mix dry ingredients together.
3. Add the butter. The butter wasn’t a dry ingredient you idiot. Rub the butter in the dry ingredients between your fingers.
4. Add milk and honey. Stir using a wooden spoon.
5. Turn dough out onto a lightly rice floured piece of 12x16 parchment paper. 12x16 of what? Don’t know, could be inches, fingers, penises for all I know, just cut a piece of paper as big as your baking pan.
6. Pat dough into a rectangle. Dust the top of the dough lightly with rice flour.
7. Place another piece of 12-by-16-inch (see inches, I told you) parchment paper on top of the dough. Roll dough out until it covers all of the paper, it won’t work, swear. Dough rectangle will be about 1/8 inch thick, sure, in your dreams.
8. Carefully remove top piece of parchment paper. She’s right be careful here.
9. Transfer dough, with bottom parchment paper, to a 12 x 18 baking pan. If your baking pan isn’t 12x18 you fail, unless you happen to have a metal saw and a demoniac grin.
10. Using a pizza wheel, score the dough into rectangles. (The rectangles should be 6 x 2 3/4 inches large for “standard” graham crackers and 3 by 2 3/4 for a “s’more” size graham cracker. My brain hurts now.) The graham crackers will break apart after baking. Do not worry if the dough seems to still be touching after scoring with the pizza wheel, that is why it said ‘score’ and not ‘cut all the way through’.
11. Prick dough all over with a fork. Vent your frustration in the process.
12. Chill dough for 10 minutes. 
13. Bake for 15 minutes or until evenly brown. It gets from brown to disgusting very quickly, beware.
14. Remove graham crackers from the pan and place on a wire rack to cool. (I slide the parchment, with the crackers, directly onto the cooling rack.)
15. Allow crackers to cool completely. Break along scored lines.

Sign of success : edible and fantastic woo-power over all coeliacs.