Use the cake pan as a pattern when rolling out fondant to cover unusually-shaped cakes. Measure pan at widest and longest areas, add 2 or 3 inches along sides for adequate coverage.
Steps:
step 1: prepare & cover cake
Prepare cake by covering with a thin layer of buttercream icing. Roll out fondant and cover cake. Smooth fondant over details on cake and trim at bottom border.
step 2: mold fondant details
Now you will add details (facial features and paws): Dust inside of pan with confectioners’ sugar to prevent sticking. Mold fondant into detailed areas of pan, press to smooth and carefully remove from pan.
step 3: attach fondant & add details
Position molded fondant pieces on cake. To attach to fondant cake, brush back with water. Fondant trims can be placed directly on buttercream cakes. Finish decorating using buttercream icing.
Source:wilton