Pat chicken breast pieces dry with paper towels and season evenly with salt and black pepper.
Heat 1 tablespoon of olive oil in a large skillet or wok over medium-high heat.
Add chicken to the skillet in a single layer and cook until browned and the internal temperature reaches 165°F (74°C), approximately 8 to 10 minutes. Remove chicken from the pan and set aside.
Add the remaining 1 tablespoon of olive oil to the same skillet.
Add broccoli florets and 2 tablespoons of water to the pan; cover with a lid and steam for 3 to 4 minutes until tender-crisp.
Remove the lid and stir in minced garlic and red pepper flakes; sauté for 1 minute until fragrant.
Add the baby spinach and the cooked chicken back into the skillet.
Toss all ingredients frequently until the spinach has wilted, approximately 2 minutes.
Drizzle with lemon juice and serve immediately or portion for meal prep.