2 (3.75-ounce 2-layer) tins brisling sardines in olive oil

2 tablespoons finely chopped parsley leaves, divided

1 tablespoon sherry vinegar

1/4 teaspoon lemon zest, reserve the lemon and cut into 4 wedges

Freshly ground black pepper

4 (1/2-inch) thick slices crusty bread, such as sourdough, country loaf or rye

1 ripe Hass avocado

Coarse sea salt