Whats the best material to use on a summer snowboard/ ski sesh?

Hopefully someone must know something about this...I'm making a summer setup in my backyard, I got my rail, and I got a platform about 4 feet high off the ground with a ramp going down to the rail. I just want to know what is the best type of material to use on the surface (to slide down on)??? I know theres astro turf and some type of fencing. But whats the fastest?? thank you