I would do the 4th side. Another consideration is wet epoxy is slicker than wet ice. Hopefully you incorporated some shark grip into your step.
Satin is a look, epoxy is slick as ice. Get it wet and you go surfing, well maybe, likely just falling.Sanded to a satin finish, but maybe that s still too slick?
Another option is to make the step out of matching wood type, but make a slatted style step. Then use the nice slab for something like a bath tray?You may be right, SteveN. Probably should have thought this one through a bit more…