If using nuts, seeds, or grains, put them in your spice grinder or small food processor and whiz until powdered or beginning to take on a thick butter consistency, about 1 minute.
Put the ground nuts, seeds, or grains, or the nut or seed butter, in your blender and add the water and salt (if using). Once you get used to this recipe, you can adjust the liquid amount up or down to suit your desired consistency. Blend for 30 to 60 seconds, or until creamy.
If desired, pour the liquid through a sieve lined with cheesecloth or a nut milk bag to remove any remaining nut bits.
If using any optional add-ins, return the milk beverage to your blender, add your chosen ingredients, and blend until smooth, about 30 seconds.
Store in an airtight bottle or container in the refrigerator for up to 3 days. It will settle and thicken as it sits. Simply thin with more liquid, if needed, and give it a quick blend