Whisk together 1 tsp. each salt and pepper, the soy sauce, and 6 tbsp. orange juice in a small bowl.
Make deep slices 1/2 to 3/4 in. apart across the grain into one side of flank steak, making sure not to cut all the way through and leaving a 1/4 in. uncut edge around steak. Stuff slices evenly with garlic. Arrange half the orange slices in a 9- by 13-in. baking dish and set steak, garlic side up, on top. Arrange remaining orange slices over meat and pour soy marinade over them. Cover dish and chill steak at least 3 and up to 24 hours; let stand at room temperature during last 30 minutes.
Heat a grill to high (450° to 550°). Skewer artichokes on two 10-in. metal skewers, brush with 2 tbsp. oil, and sprinkle with a little salt and pepper.
Oil cooking grate with a wad of oiled paper towels, using tongs. Lay steak on grate, garlic side up (discard oranges); grill, covered, carefully turning once (some garlic will fall out), 6 to 8 minutes total for medium-rare. Transfer steak to a board, tent loosely with foil, and let rest 5 minutes.
Meanwhile, grill artichokes, turning once, until lightly browned, about 6 minutes total. Transfer to a plate and remove from skewers.
Whisk together remaining 1/2 tsp. each salt and pepper, 1/4 cup orange juice, and 1/2 cup oil, the orange zest, and vinegar in a small bowl. Thinly slice steak diagonally across the grain.
Toss baby greens, arugula, chickpeas, green onions, and parmesan in a large bowl with about half the dressing. Transfer salad to a platter or plates, top with steak and artichokes, and drizzle with remaining dressing.
*Silverskin is the thin, shiny connective tissue on the outside of the meat that gets stringy when it cooks. Remove it with a sharp knife, or ask a butcher to do it.