In a large bowl, combine the masa harina and salt. Then, add the hot water and olive oil. Stir to combine, then shape it into a ball with your hands. Let the dough rest for 15 minutes. Preheat the oven to 400 F.
Divide the dough into 12 sections, and roll each one into a ball. Flatten them out into 5-inch-wide circles with your hands, or with a tortilla press. They should be at least ¼-inch thick.
After you flatten the sopes, pinch the outer edges up to create a rimmed border. Put the sopes on 2 large baking sheets that have been lined with parchment paper, and bake for 5 minutes.
While they are cooking, warm the refried beans on the stovetop or microwave oven. When the sopes are done cooking, top with beans, cheese, lettuce, tomato, onion, and avocado, and serve.