Flat Belt step pulley

I would think that is somethingyou'd turn on a lthe. Assuming you have a lathe to build a lathe

There are myriad of cog belt pulleys available. Could probably stack a few of those to get a multistep. Probably better traction than a smooth, anyway. Respectfully, Ron Moore

Buy a South Bend horizontal drive unit? Those have flat belts, or many did anyway. 4 steps. Or buy a huge chunk of aluminum and just turn one. I turned a 4-step V-belt pulley once, came out great.
GWE

You really don't need to cast them. Depending on the size wood will work well. Too small or too narrow are limiting factors for wood pulleys. You can make good pulleys out of maple. Laminated maple even better. Other hardwoods as well.Turn the hub out of aluminum and mount it to the wood using epoxy and screws. The screws really only help when the epoxy is setting up and if the epoxy ever fails. You can either use a large diameter hub or use a smaller diameter with large diameter flanges. I'd go with the flanges. One way would be to drill and tap holes into the faces of the hub and screw the flanges to the faces. The hubs can be keyed easily because they are made from aluminum. Be sure to finish the wood with a product that not only seals but also wears well. I imagine some kind of floor stuff would be ideal. ERS