Place the frozen mango, strawberries, pineapple, and banana in the blender. Let the frozen fruit sit for a few minutes so that it softens slightly - it will be easier to blend.
Add the ground flax seed and non-dairy milk, and blend on high speed until very smooth.
Pour into a glass and top with blackberries, chia seeds, or anything else you desire!
Notes
To really up the vitamin C content, you can use orange juice instead of non-dairy milk.You can use fruit that isn't frozen, but your smoothie won't be thick and creamy.Drink immediately - it will separate if you try to save it in the refrigerator.