Toast the piece of bread until the bread is just golden brown.
For the avocado, remove the pit from the avocado and discard. Remove the avocado from the skin and place the avocado flesh into a medium bowl and mash it with a fork and a squeeze of the fresh lemon juice. Season with salt and pepper as needed.
Slather the mashed avocado on top of the toast, followed by various toppings. Serve immediately.