Prepare the Tempeh Bacon:
In a small bowl, whisk together the soy sauce, maple syrup, smoked paprika, and liquid smoke.
Marinate the sliced tempeh in the mixture for at least 10 minutes, ensuring all pieces are well coated.
Cook the Tempeh:
Heat olive oil in a skillet over medium heat. Add the marinated tempeh slices and cook for 2–3 minutes per side, until golden and slightly crispy. Remove from the skillet and set aside.
Toast the Bread:
Toast the bread slices to your desired level of crispness.
Assemble the Sandwich:
Spread vegan mayonnaise on one side of each slice of bread.
Layer lettuce leaves, sliced tomatoes, and cooked tempeh bacon on four slices of bread. Add avocado slices if desired.
Top with the remaining slices of bread to complete the sandwiches.
Serve:
Slice each sandwich in half and serve immediately. Enjoy with a side of chips, soup, or a simple salad.