Procedure:

1) Place oven rack in a middle slot. Place pizza stone or steel, or a cookie sheet, on the rack. Heat the oven to 425 F.

2) Use a sharp knife to cut slices across the end of the butter stick. Each slice should be about as thick as 4 credit cards pressed together - 1/16 inch. Toss the slices into the flour as you work. Use a fork to lightly stir the slides until they're covered with flour. See left-most photo.

3) Use your fingertips or the heel of your hand to press the butter pieces into thin flat flakes. Spill the flaked butter + flour out onto a plastic work surface and shape into a "hill" with a "crater" on top. Pour the buttermilk into the “crater". (See second photo from the left). Use a bench knife or spatula to move flour/butter mixture up the sides of the "hill" and into the crater, until all the liquid is covered. Press gently down on the "hilltop" with your hand, then gently tap the flour/butter/milk blend into a rough rectangle. 

What you have at this point will not look or feel like dough. (See third photo from the left). You'll need to perform a series of letter folds to distribute the liquid throughout the dry ingredients and make a dough. The letter fold method keeps butter in flat thin pieces that will expand rapidly in the hot oven, making a light, puffy cracker, while distributing the buttermilk thoroughly.

4) Run a bench knife or spatula under the rough rectangle to loosen the dough from the work surface. Fold the top 1/3 of the rectangle down over the center 1/3, then fold the lower 1/3 up over the other two. Turn the folded dough 90 degrees, then tap with your hand into another rectangle and perform another set of folds. 

Liquid distribution will occur slowly - it may take as many as 6 fold sequences to end up with an evenly-wetted dough. (See fourth photo from the left).

5) Lift the dough from the work surface and dust the work surface liberally with gluten-free flour. Place the dough onto the dusted work surface, (See fifth photo from the left) sprinkle the dough with more flour, and roll the dough to 1/8 inch thick (the thickness of 6 to 8 credit cards). You will need to frequently slide the bench knife or spatula under the dough to be sure it is not sticking to the work surface. 

6) Sprinkle the dough with coarse salt and/or seeds (sesame, poppy, nigella, etc.) and gently roll these into the dough. Use a pizza cutter or sharp knife to cut cracker shapes. Any size will do - it's up to you! Just keep in mind that they will be quite tender when freshly baked, so smaller is smarter. (see last photo on the right)

7) Transfer the crackers to a thin flat piece of metal or thin cardboard. Tip the crackers directly onto the hot pizza stone or cookie sheet, making sure they come to rest in a single layer. Bake 7 minutes on a stone or 9 minutes on a cookie sheet, or until the edges are lightly tinted brown. Note: over-baking can happen VERY quickly, so watch closely. Remove to a cooling rack and allow to cool about 10 minutes, after which they should be cool enough to eat.