I use the acryla-miser. All of the little paint trays can be removed and it has a separate palette that goes on top for the paint you are using. You can save your mixes on the small trays. I really like it. Here is more info.
http://www.jerrysartarama.com/discount-art-supplies/painting-supplies/palettes/air-tight-palettes/acryl-a-miser-air-tight-palette-system.htm

I use the Masterson palette keeper and the Masterson Sta-Wet palette. In the latter case I toss the sponge and palette paper (can’t stand the stuff). I drop a piece of plate glass (gently) into the bottom of each and lay out my paints on a damp paper towel or cloth placed along the edge.

I have kept paints workable for as long as 3 months or so this way. Mixes are a bit more problematic, but as long as I keep them scraped up in good piles and spritzed they stay workable for several days. I also have used the little dixie cups with lids (like ketchup used to come in at restaurants) for mixes too, but found that harder to work with than the benefit it provided keeping my mixes workable.

Andrew

I just recently started painting with acrylics and I use the Masterson Sta-Wet Premiere palette, it’s 12″ x 16″. It’s great for dragging paint back and forth to classes and workshops and using the sponge & palette paper, I’ve kept paint in it for as long as 8 weeks just fine.

I have recently been intrigued by the idea of using glass for a palette, and never even thought about using the Masterson box to hold it. What an awesome idea! Thanks Andrew!!

https://www.joannenemeth.com/

See here for making your own.

Air tight container in a size of choice is basically all you need plus paper towel and mister ……. baking parchment is good for putting the paint on in little (or big) piles.

Autoslip made a good suggestion which I use – laminate an A4 piece of paper to use for mixing – easy-clean, easy to replace when necessary.

Incidentally, I use an A5 size mixing area and just clean off when dry – don’t need more!

A piece of sponge in the box keeps all my paint piles wet. I don’t worry about having one near each pile. I tried using a palette with wells but did not like cleaning them… too hard a time consuming. Easier to just scrape the glass after misting the leftover paint, it softens up and comes off real easy. Hope that helps.

The glass I use was a piece out of an old frame… not very thick, around 1/4″ or less. The edges can be sharp but you can use sand paper to smooth them down, especially if you use the glass on your desk top without the palette. Give it a try to see if you like it. Cheeper than buying lots of different palettes!