Preheat the oven to 400ºF and grease a baking sheet with olive oil. Slice the sweet potato into 1/2-inch rounds, then arrange them in a single layer on the baking sheet. Sprinkle lightly with salt and pepper, then bake them for 15 minutes. When the timer goes off, use a spatula to flip each slice and return to the oven to roast until tender, about 10 to 15 minutes more.
While the sweet potatoes are cooking, prepare the vegan cheese sauce if you haven't already, and set it aside until the sweet potatoes are done. You can use any remaining time to chop your nacho toppings, like green onion or avocado.
When the sweet potatoes are fork-tender, arrange them on a large serving platter and top them with a generous drizzle of cheese sauce, followed by black beans, jalapenos, green onions, and avocado. (Or whatever you want to use!) Serve warm. While you can pick these up with your fingers, they are not crispy like deep-fried chips, so you might prefer to use a knife and fork instead.