Turn crockpot on low heat.
Trim 3.5 lbs chicken breasts, roughly 5 breasts.
Season chicken on both sides with garlic powder, salt and pepper. Set aside.
To the crockpot add cream of chicken soup, chicken stock, Better than Bouillon chicken base, dry onion soup mix, garlic powder, pepper, dried oregano and ground thyme. Whisk until fully combined.
Add chicken to the crockpot and submerge fully in the sauce.
Add diced onions to the crockpot.
Cover and cook for 6 hours.
Remove chicken from the crockpot.
To a bowl add corn starch. Add 4 tablespoons of sauce from the crockpot to the cornstarch and mix until fully incorporated and smooth. Pour into the crockpot and turn to high heat. Cover.
Shred chicken. Add back to the crockpot once the sauce has thickened some.
Stir together and turn on warm if not ready to serve.