In a large heat-resistant mixing bowl, whisk together the cornmeal, salt, sugar (if using), and flour until well combined. Make a well in the center of your dry ingredients.
Carefully pour the boiling water into the well you've created in the dry ingredients. Let the mixture sit for 30 seconds before stirring.
Using a wooden spoon, stir the mixture vigorously until all dry ingredients are incorporated and you have a thick, smooth batter. The consistency should be similar to thick mashed potatoes.
Allow the batter to rest for 5 minutes to let the cornmeal fully absorb the water.
In a large cast-iron skillet, heat the oil over medium-high heat until it reaches 350°F (175°C). Test by dropping a tiny bit of batter into the oil—it should sizzle immediately and float to the surface.
Using a ¼ cup measuring cup or an ice cream scoop, portion the batter and shape into patties about ½-inch thick with slightly wet hands. Carefully place 3-4 patties in the hot oil, being careful not to overcrowd the pan.
Fry the patties for 3-4 minutes on the first side until deeply golden brown. Flip once using a slotted spatula and cook for an additional 2-3 minutes on the second side.
Remove the patties with a slotted spoon and place them on a paper towel-lined plate to drain excess oil. Serve immediately while hot and crispy.