5 gallon paint or pickle buckets !!!!
Freeze a gallon jug of water , place it in the 5 gallon bucket on the bottom
Have a Sealable lid and it helps to wrap the outside with foil
Those grocery store insulated bags will extend the chill if you use them as a wrap around coolers or other containers.
I’ve got two gallon-sized jugs of water in the freezer right now - one for the freezer and one for the fridge part - a block if ice that size stays frozen longer than the same volume of cubes/crushed.