Fit a piece of upholsterer's foam to fit a plastic container.
Make it a snug fit, especially not too loose.

The clay sits in the damps sponge until it is soft
enough to knead

- Hold the sponge under the tap until it holds all the water it is able to.

- Put the wet sponge back into the container, make sure there is no visible water in the container, all the water should be held in the sponge.

- Dip the piece of clay into water and make sure it is wet all over, a dry piece of clay sometimes repels the water.

- Take a look after about 20 minutes how soft the clay has become, don't let it get too soft. Leave a little longer if necessary.

A thin piece of clay (3-5 cards think) takes me about 30 minutes to reclaim. This is just a guide, times will vary with different pieces of clay.
Thicker pieces work better if the sponge is a little dryer and the piece left in longer (up to 24 hrs)

This method seems to work better with PMC than Artclay, maybe there's a difference in the binder composition that accounts for that.

I never wash the sponge, the thin clay layer that forms stops sticking for subsequent pieces.