Replying to Backyard/summer setup box/rail material preferences

Def building a little summer setup this year to play around with and keep the kid's interest all year. For boxes--what do you all prefer? I was thinking of trying plexiglass (or some similar salvaged material) glued onto a wooden box for that buttery slide. I've also seen people do multiple PVC pipes rafted together for a flat-top result. Any other ideas?

And for boxes and rails, does anybody slick the surface with anything (spray silicone or something) to mimic icy features?

Ya, it's early. But the daffodils are about to pop up and tell us east coasters the season's over.