In a large mixing bowl, combine the whole wheat flour, vital wheat gluten, sunflower seeds, flax seeds, and salt.
In a separate bowl, whisk together the nonfat Greek yogurt, warm water, and instant yeast until the yeast is dissolved.
Pour the wet ingredients into the dry ingredients and mix until a dough forms. If the dough is too dry, add a splash more water; if too sticky, sprinkle in a bit more flour.
Knead the dough on a lightly floured surface for about 5-7 minutes until it becomes smooth and elastic.
Place the dough in a lightly oiled bowl, cover with a clean towel, and let it rise in a warm spot for about 1 hour or until doubled in size.
Once the dough has risen, punch it down and shape it into a loaf. Transfer the loaf to a lightly greased baking pan or a lined loaf tin.
Preheat your oven to 375°F (190°C). Let the shaped dough rest for an additional 10 minutes in the pan.
Bake the bread in the preheated oven for 25-30 minutes until it is golden on top and sounds hollow when tapped on the bottom.
Remove from the oven and let it cool on a rack. Slice and serve once completely cooled for the best texture.