Place chicken on a cutting board and cover with saran wrap. Using a meat mallet or the bottom of a skillet, pound until chicken it is an even 1/4-in thick. Discard the plastic wrap, then cut chicken into 1-inch cubes.
Place the cubed chicken in a large bowl and add 2 tbsp of the avocado oil, the salt, pepper and arrowroot. Toss until well combined. Set aside.
In a separate small bowl, combine the coconut aminos, fish sauce, garlic, rice vinegar, ketchup, cayenne, chili flakes, toasted sesame oil, pineapple juice and arrowroot. Whisk until well combined and the arrowroot has dissolved in the mixture. Set aside.
In a large skillet over medium-high heat add your remaining 2 tbsp of avocado oil. Once heated, add your chicken in a single layer (You'll likely need to do this in 2 batches) and cook until a brown crust forms on both sides and the chicken is cooked through; about 3 minutes on each side. Transfer the cooked chicken to a clean plate and set aside until all of your chicken is cooked through.
Once all chicken is browned, add it back into the hot skillet. Whisk the sauce once more to ensure it's well combined, and pour into the skillet with the chicken. Add about 3/4 of the green onions (reserve the rest for garnish) and cook, stirring, until sauce thickens and chicken is well-coated in the sauce, 3 to 4 minutes.
Serve as desired and top with remaining green onions. enjoy!