Openforge Organizer 4x4
I made these organizers for my Openforge terrain case. I use a train case (like what makeup artists and hairstylists use) but it was always kinda a mess inside. These are meant to be stackable and can hold 7 layers of 4x4 Openforge tiles. I think it does a good job of holding them all in place. I gave it a little wiggle room, but if you wanted to try to size it down that might fit your needs better (no pun intended)
There are holes included because I plan on potentially using some sort of cord or wire to create a more accessible handle, but so far not having it hasn't been a big deal. I included options without handles and/or without holes to meet your needs better. (Pictures included are just the regular model)