Season the chicken breast evenly on both sides with garlic powder, dried oregano, sea salt, and black pepper.
Preheat a grill pan or outdoor grill over medium-high heat and lightly coat with a small amount of oil if needed.
Grill the chicken for 6 to 7 minutes per side, or until the internal temperature reaches 165 degrees Fahrenheit and the outside is nicely charred.
While the chicken rests, whisk together the olive oil and lemon juice in a small ramekin to create the dressing.
In a large serving bowl, combine the baby spinach, halved cherry tomatoes, sliced cucumber, and finely diced red onion.
Slice the grilled chicken into strips and arrange them over the bed of vegetables.
Top the salad with sliced avocado and almonds, then drizzle the lemon vinaigrette over the top just before serving.