In a large bowl, add the strawberries and squeeze about half of the juice of half a lemon (save some for the cucumber), ¼ teaspoon salt, and toss gently to coat. Transfer to a serving platter. In the same bowl, add cucumber and squeeze the rest of the juice from the ½ lemon, ¼ teaspoon salt, and toss to coat. Scatter onto the platter. Add avocado to the bowl and toss with the juice from the other half of the lemon and sprinkle with ¼ teaspoon salt. Scatter over the cucumbers/strawberries and gently mix it in.