Place chicken and mayo in a small bowl. Stir to combine the chicken salad, then season with salt and pepper to taste (if desired).
Wash and dry the spinach (skip if it came pre-washed). Wash, dry, halve, and pit avocado; using a spoon, scoop out the flesh and thinly slice.
Layer the bottom half of each bun with spinach, chicken salad, and avocado. Close sandwiches with remaining top of each bun.
To serve, divide sandwiches between plates. Enjoy!
