Halve and pit the avocados, then place the flesh in a medium bowl and lightly mash with a fork, leaving some texture.
Add the shredded chicken, chopped hard-boiled eggs, chopped sun-dried tomatoes and about 2 tablespoons of the oil from the sun-dried tomato jar to the bowl.
Stir in the crumbled feta, chopped fresh herbs, and the juice of 1 lemon.
Season with a pinch of kosher salt and a few grinds of black pepper, then taste and adjust seasoning as needed.
Toast the whole grain bread, then spoon the avocado chicken salad onto slices, top with fresh arugula or microgreens, and finish with another slice of toasted bread to make sandwiches.
