Take a fork and stab all over your flank steak. Season both sides of it with kosher salt and pepper. Place it in a ziplock bag with 1/4 cup olive oil and 1/3 cup soy sauce. Shake it to combine well and allow it to marinade for at least 30 minutes at room temperature OR (preferably) place it in the fridge and let it marinade for a few hours or all day. Just be sure to take it out 30 minutes prior to grilling so that it cooks evenly.
Meanwhile, combine all "for the sauce" ingredients in a blender or food processor. Blend until smooth. Set Aside.
Grill or sear in a skillet to desired doneness over medium-high heat (we did ours about 5 minutes per side but yours will vary depending on the size and thickness of your steak and how you like yours cooked!) At the same time, Drizzle your corn with a little olive oil and rub so that it is evenly coated. Season lightly with salt and pepper--grill your ear of corn on all sides for about 2-3 minutes per side. Remove from grill and set the steak on a cutting board. Cover with foil and let it rest for a minute while you prepare your salad.
Using a knife, gently cut the corn kernals off of the ear of corn.
Amongst bowls, divide the greens, the corn, avocado, onions, tomato, and cucumber evenly.
Slice the flank steak very thinly against the grain and serve over the salad.
Drizzle all contents of the salad with the spicy cilantro sauce.
Serve and enjoy!