Set your oven to 400°F (200°C). Use a fork to pierce sweet potatoes all around about an inch apart. Place them on a parchment-lined baking sheet and brush lightly with oil. Bake until soft when pierced with a fork, about 40 minutes to an hour depending on size.
In a mixing bowl, toss together black beans, chopped tomatoes, corn, cilantro, red onion, and garlic. Add lime juice and olive oil, then season with sea salt, pepper, and chili flakes. Stir well to combine all ingredients.
For the guacamole, mash the avocado with lime juice and a pinch of sea salt until creamy.
Whisk together coconut yogurt, lime juice, and sea salt in a small bowl to make the vegan sour cream.
Once the sweet potatoes are cool enough to handle, cut them in half. Spoon the black bean medley generously into each half. Dollop with guacamole and finish by drizzling the vegan sour cream on top before serving.