Put the almonds in a large bowl and cover them with the hot water. Allow the almonds to soak for at least 10 minutes but up to 30 minutes. Strain the almonds to discard the brown water and transfer the almonds to a blender.
Cover the almonds with 4 cups water (reserve 4 cups for the next batch). Blend on high for 1 minute then strain the almond mixture through a nutmilk bag held over a large bowl. Return the pulverized almonds to the blender and fill with the remaining 4 cups water. Blend for 1 minute, then strain through the nutmilk bag over the bowl again. Squeeze to extract as much liquid as possible.
Pour the almond milk into a large pitcher and add salt. Stir and refrigerate for up to 4 days. If the almond milk settles, stir before pouring. You can add sweetener or spices at this point, if desired.