build a frame out of 2x4s with 3/4 inch plywood on top, build a ladder into the frame if its really high. Then after you have a platform use 4x4s to make a frame for the ramp. cover that in 3/4" as well. After the platform is buillt its kindof a bitch to get a good material to ski on in small amounts. Wet leaves work but are a pain and wont stay in one place. HAve fun
===>~~~~jaxxxon