I've done this activity before and it's complexity depends on what kind of animal your mask should look like. An elephant is a good choice for starters. First, you need to cut out strips from a strong box and create the mask's frame. Finalize the frame with a bunch of used newspapers and glue. Add a pair of huge ears and a trunk to achieve the elephant-look. Paint the mask first with white and apply and apply any color that best fits your taste afterwards. Do it with your kid to make the activity much enjoyable. Have fun and good luck!