Is your loincloth based on this one from the film?

Yes, that's the one. Also the same kind they wear in The Giant of Marathon. Mine is a little less baggy than the one Hercules is wearing but in Jason and the Argonauts but I think I figured out how it folds and ties so that it knots together in the front.
For all I know it might not be the exact same way it's tied in those movies but it seems to work so I'm happy with it.