What you need - shaving foam (white shaving foam, blue shaving gel won't really work!), a tray of some sort - I used a paint roller tray, a block of ice frozen over night in a tub, some little people/animals to play with and anything else to make a set for them, eg a house/trees/cars.
Then cover the whole tray in foam, including the toy houses/cars/trees.grass etc. Pop the ice out the tub - this becomes the ice rink for the characters to skate on.
This activity is lots of fun, and very messy!
Can talk about the properties of ice "slippy, hard, cold, melts" etc. The shaving foam is good for making patterns/writting letters in with fingers. Lots of fun can be had hiding the toys under the foam and trying to seek them out again!