Faux stones for what purpose? Where and how will they be used?
Please tell us a little more about your project so that we can try to answer your question.
Large or small you don't say, but it should be easy if you use moulding clay, or stiff concrete mix with a plasticiser added. You could use Postfix too. Have fun!
Here's a post that might help - https://www.instructables.com/id/Making-Faux-StoneBrickBlock-Walls/
maybe this will help