Toast the bread: Place the bread slices in a toaster or under a broiler set to high. Toast until deep golden brown with the edges just beginning to darken. The bread should feel firm and dry all the way across when pressed lightly.
Mash the avocado: Halve the avocados lengthwise, remove the pits, and scoop the flesh into a bowl. Add the lime juice, grated garlic, and sea salt immediately. Mash with a fork until chunky-smooth. Taste and adjust salt and lime before assembling.
Assemble: Spoon the avocado mixture onto each slice of hot toast and spread to the edges, about 1cm deep. Use a generous, slightly uneven layer rather than spreading thin.
Add toppings and serve: Arrange toppings over the avocado while the toast is warm. Finish with olive oil, flaky sea salt, and cracked black pepper. Serve within 5 minutes.