Gently warm olive oil in large heavy-bottomed sauté pot. Add fennel and onion, season generously with salt and pepper. Let them relax and soften and bring them to the edge of browning, until they’re translucent and unctuous (have a greasy or oily feel).
Add garlic. (Why now? Because the slices are apt to burnt if you put them in with the fennel.)
Add lemon peel and red pepper flakes (if you like things spicier add the red pepper flakes with fennel and onion). Season generously with salt and pepper.
Once the garlic is soft (it will be moments rather than minutes), add shellfish, let them sit for a few minutes to get used to the heat.
Season monkish with salt and pepper and add to pot (if using a more delicate fish like hake or seabass, wait until broth is simmering). Stir gently; when the monkfish start to change color, add broth and raise heat to a full medium. Bring to a simmer. Once the shellfish has opened and the monkfish feels solid, slide in the scallops (if using cooked lobster, flaky fish such as hake, haddock or seabass, now is the time to add that).
Once the last batch of seafood is cooked through, ladle into warmed bowls. Top each with a flurry of fresh herbs, a pinch of flaky salt, a drizzle of olive oil, and a squeeze of fresh lemon.
Serve with thick slice of toasted bread rubbed with garlic and drizzled with olive oil and salt—or not; hunks of bread will do just as nicely, as will steamed potatoes if you are avoiding gluten.