Made a box for the ring I have for my wife. On the bottom I had her constellation made as well as the date I asked (or was going to ask).... Don't worry, she said yes. I made it out of Polywood which worked amazingly and the hinge is 2mm so a piece of polywood filament will fit through, just melt the ends a bit.
The holder fits size L (UK) but can be resized
I uploaded a plain on and the moon and stars one, but the bottoms are all blank. Please, i encourage you to take the file and customise it with something meaningful to your loved one... just make sure you throw me a tag in the remix.
update fixed the 2mm gap in the lengths of the hinge wings.