Start by chopping the carrots, potatoes, celery, and onion into roughly 1-inch pieces to ensure even cooking and a rustic look.
Add the chopped carrots, potatoes, celery, and onion into the crockpot. Pour in the diced tomatoes with their juice and the vegetable broth, then stir in the minced garlic and dried thyme.
Drizzle the olive oil over the ingredients, then season with salt and pepper to taste. Give everything a gentle stir to combine the flavors evenly.
Cover the crockpot with its lid, set to low heat, and cook for 6 to 8 hours. During the first 4 hours, you can check and give it a gentle stir to prevent sticking and to help flavors meld.
Once the vegetables are tender and the stew smells fragrant with a rich tomato and herb aroma, uncover and give it a gentle stir. If it’s too thick, add a splash of broth; if too thin, cook uncovered on high for 30 minutes to thicken.
Taste the stew and adjust seasoning with additional salt, pepper, or herbs if needed. Stir in chopped fresh parsley for a bright, herbal note.
Let the stew rest off the heat for about 10 minutes to settle the flavors. Then, ladle into bowls and serve hot, garnished with extra parsley if desired.