Peel and chop the carrots into bite-sized pieces, and dice the celery and onion to similar sizes. This helps everything cook evenly and makes the soup visually appealing.
Add the chopped carrots, celery, and onion to the slow cooker. Pour in the vegetable broth and stir gently to combine, ensuring the vegetables are submerged and starting to mingle with the broth.
Stir in the fire-roasted diced tomatoes, dried thyme, bay leaves, and a pinch of salt and pepper. This layering of flavors sets the base for a rich, aromatic soup.
Cover the slow cooker and set it to cook on low for 6 to 8 hours. During this slow simmer, the vegetables will soften and the broth will develop a fragrant, savory aroma.
Once the cooking time is up and the vegetables are tender, open the lid and add the chopped greens. Stir gently and cover again, letting the greens wilt for about 30 minutes.
Remove the bay leaves, taste the soup, and adjust the seasoning with more salt and pepper if needed. For added richness, drizzle in a tablespoon of olive oil and stir through for a glossy finish.
Use a ladle to serve the steaming soup into bowls. The soup should be vibrant, with tender vegetables and wilted greens floating in a fragrant broth. Enjoy the comforting warmth!
