In a large bowl, combine the avocado oil, harissa, bone broth, salt, and pepper. Using a mandolin, slice the sweet potatoes ⅛ inch thick into the bowl. Once they are all sliced, toss them into the harissa mixture and line them tightly upward into a 2-quart baking dish. Bake the sweet potatoes for approximately one hour, you can poke them with a fork to test doneness.
In a separate bowl, combine the avocado oil, harissa paste and bone broth. Set to the side.
Toast the pistachios, sesame seeds, and fennel seeds together in a saute pan on medium-high heat until fragrant and nutty, about 5 minutes with constant stirring. Remove once toasted and pulse this mixture in a food processor or a coffee grinder, just enough to break up the pistachios and fennel seed. You still want to see each ingredient.
Once the sweet potatoes are done, top them with the harissa paste mixture, and the toasted seed mixture. Serve warm!