To remove the air from a freezer bag with a slider closing, hold the bag open at the top while slowly lowering it into the water. The pressure of the water will squeeze the air out of the bag. Just before the top of the bag reaches the water, zip it closed.
If using a freezer bag or one made of silicone, do not submerge the seal of the bag. Clip the top of the bag to the side of the cooking container ensuring the seal will not go underwater to prevent liquid from leaking into the bag.
It is important to ensure the food is fully submerged in water throughout cooking. If the food bag floats above water, use a large, heavy metal spoon, plate or any other heat resistant utensil to weigh the bag down and keep the food submerged.
To avoid risk of burn, carefully remove the bag from the water using tongs or oven mitts.