Puree cooked lentils until smooth.
Combine lentils and flax seed, followed by honey and coconut oil. Stir well.
In a separate bowl, whisk together the flours, salt, and baking soda. Combine the wet and dry ingredients and stir well to form a crumbly dough.
Gradually add water by teaspoons until dough is neither too crumbly nor too sticky. Cover dough ball and chill for 10 to 15 minutes.
Divide dough into 2 portions. Place a large sheet of parchment paper on a flat surface or countertop and dust lightly with a little buckwheat flour. Place one portion of dough on the floured parchment and then lay another sheet of parchment on top. Use a rolling pin to roll out the dough to an even thickness (about 2 mm).
To make square crackers, simply score the dough at even increments to form a grid. To make round crackers, use a round biscuit cutter or cookie cutter to cut shapes. Gather scraps of dough and roll out again to form more crackers.
Carefully transfer each shaped cracker dough piece to a parchment-lined baking sheet. If one breaks, add it to the next portion of dough and try again.
Bake crackers in batches at 300 degrees F (150 C) for 15 to 20 minutes or until mostly crisp. (To help them bake evenly, I flipped them half-way through baking.) Allow them to cool on the baking sheet to crisp up further. (Be careful not to over-bake or they will get too dark and taste bitter.)
Store cooled crackers in a tightly sealed container.