In the same pan over medium-high heat, add avocado oil. Use one hand to hold the measuring cup of flour. Slowly and gradually sprinkle the flour into the oil. In the meantime, keep stirring with your spatula with your free hand. Please note that all we are trying to do here is to keep the flour from sticking and turning into lumps. You should always keep stirring in this process and not put the flour into the oil all at once. After adding all the flour, continue to stir a couple of times and set aside for later. (If you like, discard the extra oil above the flour by using a spoon after letting it sit for a few minutes.)
Add milk, shrimp, sea salt, and stir-fried flour into the saucepan. Stir.
Watch it closely because it takes a short amount of time for milk to boil. When it does, sprinkle some freshly ground black pepper to taste and add more sea salt if desired. (I didn’t have to add additional salt.)
Transfer the chowder into a bowl and serve immediately.