Prepare the chimichurri by combining the chopped cilantro, parsley, minced garlic, dried oregano, red pepper flakes, salt, and pepper in a bowl. Stir in the red wine vinegar, then slowly whisk in the olive oil. Let sit at room temperature to allow flavors to meld.

Prepare the grill for two-zone cooking. Bank hot coals to one side for direct, high heat, and leave the other side empty for indirect, cooler cooking. If using a gas grill, turn half the burners to high and leave the others off.

Place the picanha fat-side up on a cutting board. Using a sharp knife, lightly score the fat cap in a crosshatch pattern, spacing the cuts about 1 inch apart. Be very careful to only cut through the fat, not into the meat itself. This helps the fat render and crisp.

Cut the picanha roast WITH the grain into thick steaks, roughly 1.5 to 2 inches wide. (Cutting with the grain now ensures that your final thin slices on the plate will be against the grain).

Fold each steak into a 'C' shape, with the fat cap on the outside of the curve. Run a large flat metal skewer through the meat, piercing both ends of the 'C' to secure it. Repeat, fitting 2-3 pieces per skewer.

Right before grilling, generously coat the skewered meat with coarse rock salt on all sides. Pat it gently so it adheres.

Place the skewers over the direct, high-heat zone of the grill. Sear the meat, turning every 2-3 minutes to ensure an even crust and to prevent burning. The fat will render and drip, causing flare-ups.

Once a deep, caramelized crust has formed on the outside and the fat is crispy, move the skewers to the indirect heat zone. Close the lid and cook until the internal temperature reaches 130°F (54°C) for medium-rare.

Remove the skewers from the grill and let the meat rest for 10-15 minutes. This allows the juices to redistribute.

To serve, you can either slice the meat directly off the skewer (churrascaria style) or remove the steaks to a cutting board. Slice thinly AGAINST the grain. Serve immediately with the cilantro-garlic chimichurri.