Crack egg in a small bowl, then pass it through a fine mesh strainer to remove any loose bits of egg white. Fill a wide, deep pot with water, filling it about two-thirds to the top. Bring to a boil, then reduce heat to a low simmer and add vinegar.
Using the back of a spoon, swirl the water to create a slight whirlpool. Gently lower the egg into the pot and poach for 4 minutes. Using a slotted spoon, remove egg from water. Dab extra water out by placing a paper towel under the slotted spoon.
Add egg onto a plate. Sprinkle with flaky salt, red pepper flakes, drizzle avocado oil and serve immediately with toast.