In a large frying pan over medium heat, fry the bacon, while pressing down to keep it flat, turning once, until crispy, about 10-15 minutes. Drain on paper towels.
While bacon is cooking, lightly toast the bread in your toaster, until barely golden. Spread on the mayonnaise then layer one side of each sammy with 2 leaves of lettuce, 2 slices tomato and 1/2 the avocado.
Put the bacon on top of the avocado, top with other slice of bread then cut in half and enjoy!