I have two blocks from factory pistol cartridges that I use. One on the left is empty cases and one on the right are the full ones. I do that so I do not make mistakes since I tend to daydream after the first 30 or so. Just my safety factor.
I also use this same trays when prepping cases, when they are primed, trimmed, cleaned and ready for loading I store them in the pistol trays.