I used a 2 litre icecream bucket that was half filled with damp peat moss.
I had a piece of clear Perspex on the peat moss and food was put under the Perspex. The worms would eat the food and gather on the underside of the Perspex.
The worms were fed on a dry baby cereal, which was sprinkled very lightly over the surface of the peat. The worms ate all the food before more food was added.