Season the flank steak with sea salt and black pepper on both sides.
Heat avocado oil in a cast-iron skillet over medium-high heat.
Sear the steak for 3-4 minutes per side until a golden crust forms and it reaches your desired doneness.
Remove steak from the pan and let it rest for 5-10 minutes before slicing thinly against the grain.
In a small bowl, whisk together the fish sauce, lime juice, honey, and red chili flakes to create the dressing.
In a large bowl, combine the mixed greens, sliced cucumber, thinly sliced red onion, and halved cherry tomatoes.
Toss the salad with the dressing and top with the sliced beef, fresh cilantro, fresh mint, and crushed peanuts.