Bring 2 quarts water to boil in dutch oven or large, deep sauté pan. Add salt and greens; stir until wilted. Cover and cook until greens are just tender, about 7 minutes; drain in colander. Rinse pan with cold water to cool, then refill with cold water. Pour greens into cold water to stop the cooking process. Gather handful of greens, lift out of water and squeeze until only droplets fall from them. Repeat with remaining greens. Roughly cut each bunch of greens. Set aside.

In a large sauté pan, heat garlic and pepper flakes with oil over medium heat until garlic starts to sizzle. Add greens; sauté to coat with oil. Add 1/3 cup of broth, cover and cook over medium-high heat, adding more stock during cooking if necessary, until greens are tender and juicy and most of stock has been absorbed, about 5 minutes. Serve with lemon wedges on the side.