Preparation Using sharp knife, lightly score flank steaks about 1/8 inch deep on both sides in a crisscross pattern at 1/2-inch intervals. Place steaks in 13x9x2-inch glass baking dish. Sprinkle steaks on both sides with oregano and cumin and generous amount of coarse salt and freshly ground pepper. Drizzle olive oil over both sides of steaks, rubbing oil and spices into meat. Add green onions, beer, and Worcestershire sauce, turning steaks several times to coat both sides. Cover and chill at least 3 hours, turning occasionally. DO AHEAD: Can be made 1 day ahead. Keep chilled. Prepare barbecue (medium-high heat). Brush grill rack lightly with oil. Grill steaks to desired doneness, 3 to 4 minutes total per side for medium-rare, turning steaks 1/4 turn after 1 1/2 minutes to form crisscross grill marks, if desired. Transfer steaks to cutting board; let rest 5 minutes. Thinly slice steaks across grain. Transfer to platter and serve with Aji Sauce and Colombian Guacamole.
Preparation Using sharp knife, lightly score flank steaks about 1/8 inch deep on both sides in a crisscross pattern at 1/2-inch intervals. Place steaks in 13x9x2-inch glass baking dish. Sprinkle steaks on both sides with oregano and cumin and generous amount of coarse salt and freshly ground pepper. Drizzle olive oil over both sides of steaks, rubbing oil and spices into meat. Add green onions, beer, and Worcestershire sauce, turning steaks several times to coat both sides. Cover and chill at least 3 hours, turning occasionally. DO AHEAD: Can be made 1 day ahead. Keep chilled. Prepare barbecue (medium-high heat). Brush grill rack lightly with oil. Grill steaks to desired doneness, 3 to 4 minutes total per side for medium-rare, turning steaks 1/4 turn after 1 1/2 minutes to form crisscross grill marks, if desired. Transfer steaks to cutting board; let rest 5 minutes. Thinly slice steaks across grain. Transfer to platter and serve with Aji Sauce and Colombian Guacamole.