At least 2 days in advance, tint fondant sky blue. Roll out 1/8 in. thick. Cut eight 3-1/2 in. x 3-3/4 in. rectangles. Allow to dry on cornstarch dusted cake board.
At least 1 day in advance, stamp animals onto dried fondant plaques by brushing edible color onto animal stamps and pressing onto the plaque. Cut bright green edible decorating paper into 1 in. strips; punch 1 long edge of each strip with grass border punch. Attach grass strips to plaque bottom edges, cutting to fit, with edible adhesive. Let dry.
Bake and cool 2-layer 8 in. square cake following recipe instructions. Stack cooled cake layers on foil-wrapped cake board cut to fit.
Ice cake with buttercream icing tinted to match fondant. Attach fondant plaques to sides of cake, using piping gel if needed. Add a tip 5 bead bottom border. Punch stars, diamonds and rounds from assorted colors of edible paper; attach to cake top and sides with edible adhesive.