I missed painting yesterday. It was time to clean my many black "Staples brand paper keeper" pallets. Not only do they keep the mess down, but they can be easily stored in a fridge or freezer without fear of food contamination. I think they cost around $9.00. I am pretty sure you have seen one on my easel.
Only very occasionally, if the paint is runny, does it slide around a bit. I think that's only because I am not careful, just throwing it into my backpack.
If you try it, let me know what you think!!