all depends on how much money you have to spend
1/4" ply for the core, pipe insulation (the same kind used to make boffer weapons) for the edging and camp pad for the face. Cut to preference. either paint or use tape to cover the surface for a nice finished look. Should cost less than $25. or if you can find a round saucer sled, edge it with pipe fom, camp pad on the front for safety,
I do suggest using plastic cable ties to attach your handles with if you use cloth ahndles at least. they have a very small footprint if used correctly and they don't have any dangerous protruding parts like bolts and nuts do, they are also cheap and for $5 you can buy enough to last a couple years.
Pelinderian,
OOG: Jeff Mininger