In a small microwave safe mixing bowl, add oil, ginger, garlic, soy, water, and brown sugar. Whisk well to combine, then microwave for one minute to help encourage the sugar to dissolve. Stir well.
Add HALF of the sauce to the crockpot, stir to coat the chicken. Cover and cook on high for three hours, or low for six hours. Store remaining sauce in fridge.
Right before the chicken is ready to serve, add remaining sauce from fridge to a small saucepan and heat on medium heat.
To the saucepan, add corn starch and whisk vigorously. Bring the sauce to a simmer, stirring often until thickened, about five minutes.
Using a slotted spoon, remove the chicken from the crockpot and stir into heated sauce.
Add diced green onions, serve warm over white rice or vegetables.