This is something I do generally, safe or no safe, so take it with a grain of salt...
But it seems to me that the foam type paddings and such you often find in gun cases and cabinets aren't necessarily a good idea for knives. I like to just lay the knives flat (that's to say horizontally, but of course nothing's stopping one from doing it differently) on a relatively harmless surface, like wood, without any soft padding or insulation under them. This allows for clean airflow on both sides of the blade - both the side that's facing up and the side that's facing down against whatever material the blade is lying on. In a reasonably ventilated room with reasonable humidity levels, this seems to be a good solution: no rust, but no drying of the wooden and other similar natural material handles that like a bit of moisture every now and then.
But it seems to me that the foam type paddings and such you often find in gun cases and cabinets aren't necessarily a good idea for knives. I like to just lay the knives flat (that's to say horizontally, but of course nothing's stopping one from doing it differently) on a relatively harmless surface, like wood, without any soft padding or insulation under them. This allows for clean airflow on both sides of the blade - both the side that's facing up and the side that's facing down against whatever material the blade is lying on. In a reasonably ventilated room with reasonable humidity levels, this seems to be a good solution: no rust, but no drying of the wooden and other similar natural material handles that like a bit of moisture every now and then.