Prepare the sauce by combining the coconut aminos, beef broth, coconut sugar, 2 tsp of arrowroot starch, garlic, ginger, salt and pepper. Whisk well and set aside.
Using a large deep skillet, heat 1-2 tbsp of avocado on medium heat. Add the broccoli and add a pinch of salt and pepper. Cook for 6-7 minutes or until fork tender. Remove the broccoli from the pan, set aside, and clean out the pan.
Prepare the flank steak seasoning with salt and pepper to both sides, and using a sharp knife to slice against the grain into about 1" bite-sized slices. Add the arrowroot starch to a bowl and add the steak slices, coating thoroughly.
Using the same pan, heat 2 tbsp of avocado oil. Once the oil is hot and shimmering, add about a third, or half of the steak slices. Only add enough to where your beef is in a single layer to avoid over crowding the pan. Cook for 2-3 minutes on each side until the steak begins to crisp, and repeat until all of the steak is cooked. Set aside on a clean plate
Pour the sauce mixture into the pan slowly, using a wooden spoon to scrape up any browned bits from the bottom of the pan. Allow the sauce to simmer for about 3-4 minutes or until the garlic is fragrant and the sauce thickens. See notes for a thicker sauce.
Add the sliced green onion, beef and broccoli back to the pan and reduce the heat. Toss to fully coat the beef and broccoli and serve fresh with a side of steamed rice or cauliflower rice.
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Notes
If a thicker sauce is desired, add about another teaspoon of arrowroot starch to a small bowl with a splash of water or beef broth. Whisk well and add it to the simmering sauce to thicken the sauce further.