Stir all the ingredients together in a small bowl.
To make the smoky pinto beans:
Coat the bottom of a medium skillet or saucepan with oil and place it over medium heat. Add the onion and sauté until it's soft and translucent, about 5 minutes. Add the garlic and cook until it's fragrant, about 1 minute more. Add the beans, ¾ cup water, vinegar, cumin, smoked paprika, cayenne pepper and maple syrup. Bring to a simmer, then lower the heat. Simmer, stirring occasionally, until the sauce thickens and the beans become soft and just begin to fall apart, 10 to 15 minutes, adding more water if needed during cooking. Remove from heat and season with salt and pepper to taste.
To make the shells:
While the beans simmer, preheat oven to 200°F and line a baking sheet with parchment paper. Line a plate with few paper towels.
Pour the water into a medium mixing bowl, then stir in the salt. Slowly stir in the masa harina, adding about ¼ cup at a time. Once the masa harina has all been added, knead the dough a few times with your hands. The dough should be soft and elastic. If it seems dry or cracks during kneading, add a bit more water. If it feels sticky, add a bit more masa harina.
Divide the dough into six balls. Place them on a work surface and cover them with a damp towel or plastic wrap.
Coat the bottom of a large skillet with about a tablespoon of oil and place it over medium-high heat. Uncover one of your dough balls and flatten into a four-inch circle. You can use just your hands for this, or press it down with a large flat object, like a cutting board. Repeat for one or two more of your dough balls, depending on how many will fit into the skillet without overcrowding.
Place the dough circles into the skillet and fry for about 1 minute on each side, until lightly browned and beginning to crisp. Remove the shells from the skillet and transfer them to a paper towel-lined plate. Cool for a few minutes, and once they're cool enough to handle, gently pinch or roll the outer edges upward to create a lip. Transfer the shells to the parchment-lined baking sheet and place in the oven while you make the rest of the shells.
Repeat until all of the dough is used, adding oil to the skillet between batches as needed.
Make the sopes:
Stuff the shells with smoky pinto beans. Top with the avocado salsa and your toppings of choice. Serve hot.