These things are pads of thin paper with one side coated in plastic.
https://www.amazon.com/Jack-Richeson-Matters-Palette-16-Inch/dp/B001DMMTJ4/ref=sr_1_5
It’s super handy when gluing things up or dong anything messy, you can lay down a sheet and just toss it when you’re done. Wood glue doesn’t stick to it, it peels off cleanly. I haven’t found a downside yet.
Nice, thanks for the link!
I use to use those in my oil painting class. I would fold them up and stick them in a large flat tupperware container, I could go back a week later and continue painting where I left off and still have the colors that I mixed on the palette to use.
I saw someone on YouTube use these to mix epoxy, so I bought one. I assume it’s the same idea. Haven’t used it for anything yet, as typically happens when I buy things on spec.
hehe… I’m cheap! For glue-ups, I use the lid of the machine. For epoxy and such, I use the lids of things like take-out containers, oats, tubs of hot cocoa… 
i have a huge roll of trace paper that i unroll onto a cutting matt.
I cover my workspace in freezer paper and hold it down with painter’s tape. It protects my table and is entirely disposable but is sturdier than newsprint, prevents bleed thru, and is very, very cheap.
I am cheaper than that! 