Gather your equipment: a large slow cooker, a sharp knife, a cutting board, and a stirring spoon. Make sure everything is clean and ready to go.
Peel and chop the carrots into roughly 2-cm chunks, then slice the celery and dice the onion into small, even pieces. This creates a colorful, textured base for your stew.
Peel and chop the potatoes into similar-sized chunks, about 2 cm, for even cooking and a tender bite.
Layer the root vegetables like carrots and potatoes at the bottom of the slow cooker first, then add the sliced celery and diced onions on top. This layering helps each vegetable cook evenly.
Pour the diced tomatoes with their juices over the vegetables, then add the vegetable broth, ensuring the ingredients are mostly submerged.
Add a teaspoon of dried thyme, a bay leaf, and a pinch of salt and pepper to season the stew. Cover with the lid and set the slow cooker to low.
Cook on low for 6 to 8 hours, during which the vegetables will soften and the flavors will meld, filling your home with an inviting aroma.
After 6 hours, check the tenderness of the vegetables by piercing them with a fork; they should be soft and breaking apart easily. Taste the broth and adjust seasoning as needed.
Remove the bay leaf and thyme sprig if used fresh. If you prefer a thicker stew, mash some of the cooked vegetables directly in the pot with the back of your spoon.
Stir in chopped fresh parsley for a burst of color and freshness, then let the stew sit off heat for a few minutes to allow flavors to settle.
Serve the hot, hearty stew in bowls, garnished with additional parsley if desired. Enjoy the cozy, comforting aroma and rich, well-blended flavors.