Put the almonds in a large bowl and cover with water. Let them sit for 4 hours.
Drain the almonds and discard the water they soaked in. Rinse them well under cold water.
Add them to a blender with 4 cups filtered water. Blend at a medium high speed for about 3 minutes or until the almonds are fully broken down.
Place a nut milk bag in a large bowl. Pour the almond milk into the bag over the bowl. To strain the pulp, squeeze tightly on the bag to release all of the liquid. Discard the pulp or use it in another recipe. Add the vanilla to the bowl, stir, and pour into a container with a lid. Store the almond milk in the refrigerator.