You will need a coloured canvas bag (I bought mine from http://www.[thecleverbaggers.co.uk), about 30cm square of black fabric, a smaller piece of white fabric and enough double sided iron on interfacing to cover the fabric.
Iron on the interfacing to one side of your fabric scraps
Using the template here Animal bag face template trace 1 mouth, 2 eyes, whiskers and 2 ear shapes
Peel off the backing paper and position the shapes on your bag
Iron into place