1. Toast bread until golden brown.
2. Spread mayo on one slice of bread and avocado on the other.
3. Sprinkle the avocado with flaky sea salt.
4. Place the sliced tomato on top of the mayo and sprinkle with a little more salt.
5. Add the sliced cucumber, sliced red onion, alfalfa sprouts, romaine lettuce, and Swiss cheese on top of the tomato.
6. Close the sandwich, slice it in half, and enjoy while the bread is warm and toasty!
