In a small bowl, whisk together minced garlic, grated ginger, water, brown sugar, and coconut aminos.
Ensure the sugar dissolves completely to create a smooth sauce. Set aside.
Slice the flank or skirt steak thinly against the grain into bite-sized strips. This helps keep the meat tender.
In a medium bowl, toss the steak pieces with cornstarch, ensuring each piece is lightly coated.
Season with a pinch of salt and pepper for added flavor.
Heat 1-2 tablespoons of avocado oil in a cast iron or non-stick large skillet over medium-high heat.
Once the oil is shimmering, add the coated steak pieces in a single layer.
Sear the steak, cooking for about 2-3 minutes per side, until the edges are crispy and begin to char. Avoid overcrowding the pan; cook in batches if necessary.
Remove the cooked beef from the pan and set it aside in a bowl.
In the same skillet, add a bit more oil if needed.
Add the red bell peppers, yellow bell peppers, and julienned carrots.
Stir-fry the vegetables over medium heat until they reach your desired tenderness—about 4-5 minutes for crisp-tender vegetables.
Lower the heat to medium-low and return the cooked steak to the skillet with the vegetables.
Pour the prepared sauce over the beef and veggies, stirring to coat everything evenly.
Let the sauce come to a gentle boil. Cook for 3-5 minutes, allowing it to thicken slightly. Stir occasionally to prevent sticking.
Remove from heat and serve over prepared white rice or rice noodles.
Garnish with chopped green onions and a pinch of red pepper flakes (if using) for added flavor and presentation.