I've used flax seeds many times in my smoothies. The blender chops them up nicely, to release their nutrients. I usually throw in a handful of whatever leafy green thing is in my refrigerator. Mache leaves are a current favorite of mine.

And, I'm always adding superfoods to my smoothies, like chia seeds, hemp seeds, raw cacao nibs, maca powder, spirulina, raw cacao powder, and cinnamon. Getting them as nutrient-dense and filling as possible, while still tasting good, is the key.

It sounds like you did an excellent job with your foraged food smoothie. I take nettle extract every day, but haven't tried it in its raw state yet. Maybe I will, after reading your recommendation.