Add the chopped onion, minced garlic, cubed butternut squash, and drained chickpeas to the slow cooker.
Pour in the diced tomatoes with their juices and the vegetable broth.
Drizzle the olive oil over the mixture, then sprinkle in the cumin, coriander, cinnamon, paprika, turmeric, salt, and black pepper.
Stir everything gently until the spices are evenly distributed.
Cover and cook on low for 6 to 7 hours or until the squash is fork-tender.
Taste and adjust salt or pepper if needed, then stir in half the chopped cilantro.
Ladle into bowls and serve with the remaining cilantro and lemon wedges on the side.