I've been thinking about this lately too. I have two of these that I got for my gouache paints (unfortunately discovering that if I don't paint for a few days, mold will form!):
I wonder if this would work for oils, too. There are other variations on this theme like this one:
My Masterson stay-wet palette is really big. I have been covering it with plastic wrap but this kind of makes a bit of a mess and doesn't do a very good job preserving the puddles since they stick to the wrap. I think I might try using a palette knife to scrape puddles into these boxes.
I'm not sure if the oil would start to skin over after a time. I know you can put these in the freezer to slow down oxidation as well. Does anyone else have experience with this? (I'm going to test it out this week I guess...)