You don't need the bag. The bag is to hold in moisture, but that is not needed when cooking chicken properly.
The "Secret" to Moist, Delicious Chicken
1) And this is the most important, brine the chicken for at least 3-4 hours. Preferably overnite or longer.
Simply take the chicken, once cleaned, and place in large mixing bowl completely under cold water. Add 1 full TBS of sea salt, don't worry about sodium or "salty taste" the salt is to open the pores of the chicken to allow the water to permeate the meat. Remove chicken and put spices/herbs whatever you like, or recipe calls for.
2) Drizzle the chicken with olive oil and rub into chicken.
3) For a whole chicken, preheat oven to 450. And place chicken in oven Set the timer for 15 minutes. This will sear the meat and brown the outside, and seal in the moisture.
4) WITHOUT opening oven door - turn oven down to 350. And cook until internal temp. is 165. WIll be between 40 minutes to 1 hour depending on size of chicken.
Your chicken will be perfect. Crisp on the outside, and super moist.
Don't skip any steps. It will not turn out right if you do.