Moving boxes. Any given day if you look into someone garage, you can see folks with regular moving boxes stacked in their garage.. I'm not sure about using a fridge box, that's kinda large and obvious...I mean who stores an unused fridge in their garage?
Get a couple of moving boxes, cut out the "top and bottom" on a few (leave one for the top) and a corner on all of them. Then arrange them around the safe as if they were just plain stacked storage boxes in the garage.
"Those who hammer their guns into plows will plow for those who do not."