If you don't need it to be bent then you can pour it in plaster like usual and as it starts to set up scrape some of the plaster out. I have done this with a couple of doors for my on again off again dungeon project. If you do it right it will look like something has been clawing its way through. You can add a fair amount of customizing to a door this way.

Pete
Democracy is two wolves and a rabbit voting on what is for lunch.

Liberty is a well armed rabbit contesting the vote!