Rinse the thawed frozen shrimps in a sieve and let them drain well. Rinse the salad and dry it thoroughly. Tear it into smaller pieces, depending on the type of salad you are using. Rinse the cucumber and cut it lengthwise. You may remove the seeds with a teaspoon. Slice it thinly. Cut the avocados lengthwise and remove the pits in the middle. Cut the flesh into small cubes. Immediately drizzle with a bit of lemon juice to prevent discoloration.  Arrange the salad on a large platter. Place the cucumber, avocado, and finally the shrimps on top.  Sprinkle with chopped dill and serve immediately.