Sprinkle a baking sheet with sorghum flour. Use your hands to form dough into a ball, sprinkle liberally with flour, and then gently roll dough out into a thin sheet (use more flour to prevent sticking if needed). Aim for no more than 1/8-inch thick; too thin is preferable to too thick.
Use a pizza cutter to cut into one-inch squares. Sprinkle with coarsely ground salt, if desired.
If you don't have a food processor, mix the flours and butter together with a pastry blender or wooden spoon, then use your hands to combine the butter into the flour thoroughly. Add the remaining ingredients, again using your hands to combine the ingredients well.
Keep an eye on the crackers as they cook; remove any that begin to brown before thicker crackers.