We started by placing sweet potato baby food in a ice cube tray to freeze. Once frozen we placed the cubes in a bin of cornstarch(cornflour in the uk) As the cubes melt it made a goop in the cornstarch. We ended up adding some orange dyed water to make it better. This goop is also called oobleck. It is good for sensory play and be both a liquid and solid. It is also edible so it is ok for toddler and babies who like to mouth things. We added in some leaves but that is totally optional and is just as fun without.