I have made three of these dog sleds from stuff I was going to trash. Build time is 30-60 minutes. The sleds are featherweight, durable and will provide hours of fun..
Step 1: Alpha and beta sleds
I turned the chair around on the next two and found that offers much more control. You can hold the arms to stand on the spreader bar and sit on your knees up on the chair once you're cruising.