I would like my oldest (about 3 1/2 years old right now) to carve something, because of the fun I had with my [plaster carving][1].

However, most carving requires sharp knives and firm materials that are difficult to cut through.

I would like an alternative that is soft enough to work with using just plastic tools (which I may make myself or repurpose from other tools), but not soft like Playdough or modeling clay. That is, I want it to be able to keep its shape during and after carving.

The kid-safe aspect of this is being able to avoid sharp metal objects.

Is there anything out there that would work for me?

  [1]: https://crafts.stackexchange.com/questions/1692/what-steps-do-i-take-to-prepare-a-plaster-block