Combine all the ingredients into a firm dough in a bowl. Roll into a thin sheet approximately 0.5 cm (⅛ inch) thick on a flour-dusted countertop. Cut the dough into strips or cut out shapes using a biscuit cutter. Preheat the oven to 200°C (400°F/Gas 6) and bake the doggy biscuits for approx. 30 minutes until golden brown. Keep in a sealable jar.