Add olive oil, onion, garlic, and ginger to the slow cooker.
Toss in bell pepper, chickpeas, diced tomatoes, and tomato paste.
Sprinkle in garam masala, cumin, coriander, turmeric, paprika, salt, and cayenne.
Pour in coconut milk and stir to combine everything.
Cover and cook on low for 6 hours.
Taste, adjust seasoning, and stir well.
Serve hot over rice or with naan.
Garnish with cilantro if desired.