Heat a large skillet over medium-high heat. Cut chicken in half (like your butterflying it), so that you have two thin breasts. Place chicken in the hot skillet, and cook for 3 to 4 minutes until browned. Turn chicken over, and cook another 3 to 4 minutes, until cooked through. Remove to a cutting board and cool until your can easily handle the chicken. Thinly slice the chicken breast halves.

Heat a small skillet over medium heat. Add almonds. Toast almonds, stirring occasionally, until lightly browned, 3 to 5 minutes. Remove to a bowl.

Thoroughly rinse spinach to remove any dirt. Chop spinach into bite-sized pieces. Dry spinach with a paper towel.

Place spinach, chicken, almonds, and feta in a large bowl. Drizzle with salad dressing. Toss to combine. Serve immediately.