Heat the oil in a medium skillet over medium heat. Add the tempeh bacon in a single layer and fry until cooked through, about 2 minutes per side.
While the tempeh cooks, toast the bread and spread each slice with the mayonnaise .
Top 1 slice of toast with half of the lettuce, tomatoes, avocado, carrots, sprouts and tempeh bacon. Repeat with a second slice of toast. Stack the toasts and close the sandwich with the third slice of toast.
Cut the sandwich into quarters and enjoy!
You can absolutely make your own marinade for the tempeh but for the sake of time and ease, I like to buy pre-prepared tempeh bacon.