Slice the chicken breast into thin, bite-sized strips and season evenly with sea salt and black pepper.
Heat the avocado oil in a large skillet or wok over medium-high heat until it begins to shimmer.
Add the chicken to the pan and sear until golden brown and cooked through, approximately 5 to 6 minutes.
Remove the chicken from the pan and set aside on a plate; add the broccoli, bell peppers, and snap peas to the same pan.
Stir-fry the vegetables for 3 to 4 minutes until they are tender-crisp and maintain their bright color.
Stir in the minced garlic and fresh ginger, cooking for 30 seconds until the aromatics are fragrant.
Return the chicken to the pan and drizzle with tamari and toasted sesame oil, tossing everything together to coat well.
Serve the stir-fry immediately over the warm cooked brown rice for a complete, clean meal.