1. Bring 1 inch of water to a boil in a large pan. Line with parchment a steamer basket that will fit in pan. Arrange potatoes on top; sprinkle with salt. Place salmon over potatoes; sprinkle with salt. Lower steamer into pan (don't let basket touch water). Steam for 6 minutes. Place green beans over salmon, cover and continue steaming until potatoes and beans are tender and fish is cooked through, 4 to 6 minutes longer.
2. Transfer potatoes, beans and salmon to a large bowl; flake salmon. Let cool slightly. Add olives to bowl, drizzle with oil and lemon juice, season with salt and pepper and serve.