Remove the lettuce leaves from the cores and tear them into bite-sized pieces.
Wash, spin dry and place in a large bowl.
Add the cucumber, tomato, onion slices and avocado.
Pour the lemon juice directly onto the salad and then add the olive oil.
Sprinkle the dried mint and salt over the salad, then toss until the ingredients are distributed evenly.
Substantial pieces of avocado should remain intact while just slightly coating the lettuce leaves.
Taste for salt and mint and add more, if necessary. Serve immediately.