Season the flank steak by sprinkling the seasonings evenly over the meat to taste. Side Note: I didn't measure the seasonings; I sprinkled a bit of each on both sides of the steak.
Once seasoned, place the steak on a plate, cover with plastic wrap, and refrigerate for a few hours.
Prepare the chimichurri sauce by placing the cilantro, parsley, sea salt, black pepper, cumin, white wine vinegar, and crushed red pepper in a food processor.
Pulse ingredients a few times, then while processing, slowly add the olive oil until the mixture emulsifies, about 1 minute. The sauce should be nice and smooth.
Keep the sauce at room temperature until ready to serve.
Preheat a grill pan or grill over medium-high heat.
Grill the steak for 5-6 minutes on each side, to your desired degree of doneness.
Make sure to let the meat "rest" for at least 5 minutes before slicing.
Slice the steak against the grain into thin slices.
Drizzle the chimichurri sauce on top and serve. Enjoy.