Put the porridge oats into a bowl and fill it up with water from the tap. Cover the bowl with a tea towel and let the bowl sit for 4 hours or overnight. Do not put in the fridge.
Once you have let the oats overnight or for 4 hours, take a sieve and sieve the mixture and draining the water. Rinse the oats under the tap for a few seconds.
Now, put the oats into a blender or food processor with 750ml of cold water and 1/2 teaspoon of sea salt. Blend until completely smooth with no oats visible. The more you blend, the creamier your homemade oat milk will be.
Put the sieve over a bowl or jug and let the mixture pour out. Leave to strain for about 1 hour.
When most of the mixture has been strained, take the sides of the cloth together and squeeze tightly to extract the oat milk.
At this point, you can bottle it up and keep in the fridge until you are ready to drink. If the oat milk is too thick for your liking, you can add 50ml of cold water until you reach the consistency you like.