For the people who don't have a freezer big enough like me. I use a little cotton ball with a bit of clove oil on it. Put it on the palette (I use a little slip on oil container to put the cotton ball in place and stuck to the palette). Close off your palette using this sealer et voila. Your paints won't dry/oxidize for 6 weeks at least. A little trick I learned.
Before you put the lid on the palette pull the palette paper out with the paints and ring the bulk of the water out of the sponge then put it all back together. When you get the palette back out to work you can add more water back to the sponge. This has worked well for me.