Put the sliced cucumbers in a colander with a healthy sprinkling of salt. Put the colander on top of bowl to catch the water, and put in the fridge, letting them sweat for about an hour. The bowl should catch a fair amount of water.
While the cucumbers are sweating, blanch the beans in a pot of salted boiling water: cook them for a few minutes and then plunge into ice water.
Dry the cucumbers (pressing out any extra water), dry the beans, toss together. Add chopped dill and lemon juice. The amount can vary quite a bit, depending on how much many cucs and beans you have; you can use a whole lemon or concentrated lemon juice in the fridge, but always use fresh herbs. Toss and enjoy right away -- it'll keep for a couple days in the fridge.