Since the fans are pointing out the back, I suggest simply a piece of glass. It's what I myself use. It's sturdy, doesn't mark tables, sticks to your skin if you don't want it to slide, stays cool, looks nice and lasts forever. Make sure it's shatterproof glass, something you'd use on a coffee table or a TV cabinet. I scavanged mine off of a side-table which was sitting on the side of the road, used it for 4 years.
Works on my bed, lap, anything.
It's free if you find one, obviously, give it a try, just make sure it's flat so the bottom of the laptop can always breathe under the gap.
Can use wood or any sort of plank, I just prefer something that won't bend or warp when I wash it from time to time. :3
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