Where you put the gel pack can matter as much as how many you use.
On top
Cold air sinks, so a pack placed on top of the product cools everything below it. This works well for light, delicate items such as berries and baked goods.
On the bottom
A pack underneath suits heavier, dense items such as meat and butter, which sit firmly on the cold surface.
Top and bottom
For longer routes or warm weather, sandwich the product between packs above and below. This gives the most even temperature through the whole box.
Always fill empty space so warm air cannot circulate, and tape the box closed promptly after packing.
