Dice the celery, onion, garlic, and jalapenos. Grate the carrots using a cheese grater.
Add black beans, carrots, celery, onion, garlic, and jalapeno to a 6-quart slow cooker. Stir to combine. Add salsa, cumin, chile powder, and oregano. Stir to distribute spices. Add broth and water to the slow cooker, and stir once more.
Cover and cook on HIGH for 7 to 8 hours, or until beans are tender. You should be able to mash the beans really easily when they're done.
Transfer soup to a blender (do not fill more than 1/2 way full) and pulse until the soup is almost smooth. You'll need to work in batches. You could also use an immersion blender to puree everything right in the slow cooker.
Stir the soup together and season with salt and pepper to taste.
Serve soup warm, topped with sour cream, cilantro, avocado, and/or jalapeno if desired.