In large bowl, whisk together Cassava Flour, whole and ground flax seeds, chia seeds, sea salt, baking soda, cream of tartar, and rosemary.
In separate small bowl, mix together oil, water, coconut sugar, garlic, and cayenne. Use a silicone spatula to stir oil mixture into flour mixture to form a ball of dough. Let rest 5 minutes and mix again.
Divide dough in half. Wrap one half in plastic wrap. Place other half on sheet of parchment paper and cover it with another sheet of parchment paper. Place a sheet pan on top and press down as hard as you can in the center to flatten the dough into a thin, even sheet. Remove sheet pan and use a rolling pin to roll the dough as thin as possible. Place dough, still sandwiched between parchment paper, on sheet pan and put in freezer for 10 to 15 minutes, or refrigerator for 30 to 45 minutes, until dough is stiff and firm. Repeat process with other half of dough.
Preheat oven to 300° with rack in center of oven.
When dough is stiff and firm, move it from sheet pan to a cutting surface. Remove top piece of parchment paper. With a long knife or pizza cutter, cut 1-inch-wide strips all the way across the sheet of dough. Turn parchment paper a quarter turn and repeat cutting strips the same width across the dough, to form 1-inch squares. Sprinkle with salt if desired.
Bake 30 to 40 minutes, until crackers are firm to the touch and starting to darken around the edges. Remove from oven. Separate crackers using a knife, bench scraper or pizza cutter. Remove crackers that are browned, especially on the edges, from sheet pan and set aside on a wire rack to cool; they are done. Spread the remaining crackers across sheet pan and return to oven for another 10 to 15 minutes until edges are brown and crackers are completely dry.
Cool crackers completely on wire rack before storing in airtight container lined with parchment or wax paper; they will keep for weeks in a cool dark place.
NOTE: A ball of dough wrapped in plastic will keep for 3 days in the refrigerator . If after baking crackers aren’t quite crispy enough or have gone soft overnight, spread out on sheet pan lined with parchment paper, and bake at 300° for another 10 to 15 minutes.