Mionix Microfiber Gaming Desk Pads

Fill up a sink, bucket or some kind of plastic container with warm water, add some mild dish soap like Dawn, and let it soak for a couple of hours, at least, and then take it out and scrub it with a wash cloth. Rinse it clean (I use high pressure nozzle on my hose outside) and let it air dry over night. If you have a power washer, you can simply lay it on the driveway outside and power wash the grime out of it.