Pat the fluke completely dry with paper towels — dry fish means a good sear. Season both sides generously with salt and black pepper.
Heat a heavy skillet (cast iron or stainless) over medium-high heat. Add the neutral oil and heat until it shimmers.
Lay the fluke in the pan presentation-side down: skin side if skin-on, smooth side if skinless. Press gently with a fish spatula for the first 10–15 seconds to prevent curling.
Cook 3–4 minutes, untouched, until the edges turn opaque and the bottom is golden.
Flip gently and add the butter, garlic and herbs to the pan. Tilt the pan and spoon the foaming butter over the fish for 1–2 minutes, until just cooked through.
Transfer to a plate and rest 1 minute. Finish with lemon and a final pinch of flaky salt.
