In a heavy saucepan over medium heat, warm coconut oil. When the oil starts to shimmer, add onion and red bell pepper and sweat for about 3 to 4 minutes until tender.Lower heat and add garlic and fresno pepper, and cook until fragrant, about 1 minute.Add the harissa paste, sweet potato, and drained chickpeas, and stir until the paste coats everything.Add in the crushed tomatoes and stock. Raise heat to medium and bring mixture to a simmer. Lower heat and let cook until the sweet potatoes are tender, about 15 to 20 minutes. The sauce should reduce and thicken during this time.Season with salt and pepper, and serve with a warm flatbread, greek yogurt, or extra harissa paste.