Preheat oven to 350°F. Line a cookie sheet. Process almond flour, arrowroot starch, salt, and baking soda in a food processor until thoroughly mixed. Add agave nectar and lemon zest, processing just until dough comes together. Knead in chopped almonds. Roll into 2" thick log and bake 15min. Cool 1 hr. Preheat oven to 300°F. Using sharp knife, slice every inch on the diagonal. Lay slices sideways and bake 12-15min. Cool.