In a small bowl, mix the rub ingredients until well combined. Set aside.
Pat the steak dry with paper towels. Trim it of any surface fat.
Brush it lightly with olive oil. Press the rub into both sides of the steak.
Build a charcoal fire or preheat a gas grill.
Meanwhile, make the Chimichurri Sauce: Put all the ingredients in a blender or food processor and pulse until well chopped hut not pureed.
Just before grilling, season the steak with salt.
Place the meat on the cooking grate over direct medium heat, cover, and scar. Cook for 4 to 6 minutes. Turn the steak with a pair of tongs and sear the second side. Continue grilling 3 to 5 more minutes for medium-rare. Use the A-OK method or an instant-read thermometer to test the meat.
Remove the steak from the grill and put it on a clean platter to rest for 5 to 10 minutes before carving. While the meat rests, spread the baguette slices with Chimichurri Sauce and set aside.
Cut the steak across the grain into thin diagonal slices.
Place a slice on each piece of bread spread with the Chimichurri Sauce and sprinkle with a pinch of fleur de sel.