how is the best way to create a celtic artefact from an everyday object

Answer 1

http://www.google.com/images?q=celtic+artifact&hl=en&prmd=ivns&source=lnms&tbs=isch:1&ei=YGhuTfzJPIL-8AaekfSqDw&sa=X&oi=mode_link&ct=mode&cd=2&ved=0CAoQ_AUoAQ&biw=1024&bih=481

I think I'd use a large chunk of styrofoam (that can be carved) or papier mache.
http://www.papiermache.co.uk/tutorials/getting-started-with-papier-mache/

Answer 2

I'd make homemade clay using flour.

http://clayrecipe.net/

http://www.google.com/images?hl=en&q=Celtic+artifact&bav=on.2,or.&um=1&ie=UTF-8&source=univ&sa=X&ei=u2duTcuBLImatweorrSNDw&ved=0CDoQsAQ&biw=994&bih=636