To prepare the sauce, whisk the ingredients together. Set aside.
Prepare the flank steak by using a sharp knife to slice against the grain into about 1″ bite-sized slices.
Add the steak to a bowl and season with salt and pepper. Top with arrowroot starch and toss to thoroughly coat.
Using a large, deep pan set to medium heat add 2 tbsp of avocado oil to the pan along. Once the oil is shimmering, add the broccoli and snap peas. Lightly salt and saute for 3-4 minutes. Add the bok choy and lightly saute.
Reduce the heat to low and add a splash of water (about 2-3 tbsp) and cover for 2 minutes to allow the vegetables to steam and soften further.
Remove the lid and add garlic. Saute for another 2-3 minutes or until the bok choy is softened and the garlic is fragrant. Set the vegetables aside on a covered plate ot keep them warm.
Return the pan to medium-high heat and add more oil. Once the oil is hot and shimmering, add half of the steak slices. Cook for 2-3 minutes on each side, and repeat until all of the steaks is cooked. It's key to work in batches and not overcrowd the pan!
Once all of the steak is cooked reduce the heat, and add it all back to the pan along with the vegetables and the sauce. Stir until the sauce coats the beef and vegetables.
Serve topped with green onion!