In a large skillet or wok, heat 3 tablespoons of avocado oil over medium-high heat. The oil should shimmer, indicating it's ready for cooking.
Add the finely minced garlic and ginger to the skillet. Sauté for about 30 seconds until fragrant, being careful not to burn the garlic.
Place the sliced bok choy in the skillet, cut side down. Allow it to cook for 2-3 minutes until it starts to soften and develop a bit of color.
In a small bowl, whisk together the soy sauce, oyster sauce, light brown sugar, and chicken stock (or water). Pour this mixture over the bok choy.
Using a spatula, gently stir the bok choy to coat it evenly with the sauce. Cook for an additional 3-5 minutes, stirring occasionally, until the bok choy is tender yet still crisp.
Once the bok choy is cooked to your liking, remove it from heat. Serve immediately, garnished with sesame seeds or sliced green onions if desired.