Place almonds in a bowl and cover with a couple inches of water. Soak overnight or for 8 hours. If you are in a rush, soaking for 1-2 hours works in a pinch. Drain and rinse almonds after soaking.
Place almonds in a high speed blender along with the 3 cups filtered water, chopped vanilla bean (if using), vanilla extract, and salt. Blend on the highest speed, for about 1 minute until the almonds and vanilla bean are pulverized.
Place a nut milk bag over top of a large bowl and pour the almond milk into the bag. (You can also use cheesecloth placed over a fine mesh sieve, however a nut milk bag yields the smoothest result and is faster.) Squeeze the bag and press out all the milk. The pulp will remain in the bag/cloth (you should have about 1 cup of pulp).
If using dates as your sweetener: Note: I only recommend using dates if your blender can pulverize them super smooth, otherwise use liquid sweetener. Rinse out the blender. Carefully pour the almond milk back into the blender and add the pitted dates. Blend on the highest speed until the dates are pulverized and the milk is super smooth. Add milk back into the bowl.
Whisk in the chia seeds (and the maple syrup, only if not using the dates). Place in the fridge for 2-3 hours, until thickened and cold. Give the mixture a good stir every once in a while to redistribute the chia seeds.
Chia seed pudding will keep in the fridge for up to 3-4 days. It freezes well too, just thaw in the fridge before ready to enjoy.