Replying to For those who dont know what to use for box surface material...

USE FORMICA!!

For those unfamiliar with it, Formica is used for counter tops, cabinets, etc...

It comes in sheets like plywood does, so you can cut it to any size you need.

Use contact cement to adhere it to your box.

Formica is a pretty hard surface and it slides very well. My friends and i went a step further and waxed it for optimum smoothness, but this is absolutely not necessary and will probably be too slick for some peoples liking.

It's much cheaper than HDPE and slides just the same.

And...it comes in many colors/patterns.

Hope this helps someone

enjoy.