1. Season the chicken well with salt and pepper. Place in a slow cooker and add one to two tablespoons of harissa, depending on how spicy you like things. (I don’t love spicy food, and I found that a Tbsp of harissa really just imparted the peppery flavor without much heat at all.) Pour the shakshuka sauce in the pot and cover. Cook on low for about five hours or on high for about two and a half hours. Alternately, this can be cooked covered on the stovetop over a low flame for about two hours, or until very tender.
2. Remove the chicken from the pot and shred with two forks. Return to the sauce and cook an additional 10 minutes with the cover off. (This can be made a day or two ahead and then reheated.)
3. Sauté sliced onions in oil, seasoning to taste. Set aside. In a frying pan coated with cooking spray, fry six sunny-side-up eggs until the whites are set. Toast each roll and add a few slices of avocado and pulled chicken. Top with sautéed onions and egg.