Position a rack in the center of the oven and preheat to 325ºF.
Spread the sunflower seeds, almonds, buckwheat groats, and millet seed on a rimmed baking sheet. Toast in the oven until golden and fragrant, 8-12 minutes.
Meanwhile, in a large bowl, combine the almond and chickpea flowers, flax seeds, psyllium husk, flax meal, chia seed, and salt. When the sunflower seed mixture has toasted, add it to the bowl and stir to combine. Add the maple syrup, olive oil, and water, and stir to combine well, using your hands if need be.
Line a loaf pan (8×4 or 9×5″) on all sides with parchment paper. Scrape the dough into the pan and use damp fingers to smooth the top, creating a slight dome. Cover the dough and let sit at room temperature at least 2 hours and up to 24 hours.
When ready to bake, position a rack in the center of the oven and preheat to 400ºUncover the bread and bake until deeply bronzed, about 75 minutes. Remove the bread from the oven and let cool completely, at least 2 hours, then remove from the pan and discard the parchment.
The bread keeps well, refrigerated airtight, for up to a week or even two. Slice and toast for best results.