Toast the multigrain sandwich flat to your desired level of crispiness.
While the bread is toasting, dice the avocado into cubes and flatten it onto the toasted bread using a fork. Squeeze some lemon juice on top of the avocado.
In a sauté pan, heat up some avocado oil on medium-low heat. Add the baby spinach and sauté for about 5 minutes until wilted. Add some fresh squeezed lemon juice, salt and pepper to taste.
Once the spinach is cooked, add it on top of the avocado on the sandwich.
Sprinkle feta cheese crumbles over the spinach.
Drizzle balsamic glaze over the top of the sandwich.
Season with salt and pepper to taste.