Just put containers of water to fill up as many open areas of your freezer as you can. The linked post suggests using milk bottles or orange juice containers. We use rinsed out 2-liter pop bottles.
As the link says it also helps keep your food frozen longer if you have an interruption in electricity.
We use the frozen ice in the pop bottles for road trips too. We just transfer a few pop bottles from the freezer to our cooler. (Put new ones in the freezer.) After the ice in them has melted you have nice cold drinking water in the cooler. You will have to add ice after that. When we start out we first put in the pop bottles & our jug of milk we always bring. Then we add ice cubes from our refrigerator’s ice maker. We don’t usually need to buy ice the first day. Any ice left from trips gets put in the chest freezer to use on the next trip. When dh buys ice he leaves it in the plastic bag so that it’s easier to put in the freezer when we get home.
It might seem silly to save all this ice, but every little bit helps. And with rising prices on so many things, why throw away money on ice?
Click title for link at LifeHacker.