Preheat oven to 350°F. Butter a 9-by-13-inch cake pan. Line with parchment, leaving a 2-inch overhang on long sides. Butter parchment; dust with flour, tapping out excess. Whisk together flours, baking powder, and salt.

In a mixer fitted with the paddle attachment, beat together butter, sugar, and orange zest on medium speed until light and fluffy, 2 to 3 minutes. Add eggs, one at a time, mixing well after each addition and scraping down bowl as needed. Reduce speed to low and gradually add flour mixture, beating until combined. Add milk and almond extract; beat until just combined.

Pour batter into pan; smooth top with an offset spatula. Bake until golden brown and a tester inserted in center comes out clean, 30 to 35 minutes. Transfer pan to a wire rack; let cool completely. Remove cake from pan using parchment. (Remove and discard parchment.) Cooled cake can be wrapped tightly in plastic and refrigerated up to 2 days.

Using two large spatulas, carefully transfer cake to a cake plate. Coat with a thin layer of buttercream over sides and top. Refrigerate until chilled, 30 minutes. Spread chilled cake evenly with another 2 cups buttercream, creating squared edges. Refrigerate 30 minutes.

For Gravel Path and Flower Beds: Pulse vanilla wafers in a food processor until finely ground (you should have 1/2 cup). Transfer to a bowl. Tap out bowl of food processor to remove any excess crumbs and repeat with chocolate cookies (you should have 1 cup).

To create the appearance of "gravel", combine 1/2 cup chocolate crumbs with vanilla crumbs. To create the appearance of "dirt", use remaining chocolate crumbs. Using an offset spatula, gently mark a 1 1/2-inch-wide path vertically down center of cake. Mask each side of path with pieces of parchment.

Sprinkle with cookie "gravel," extending over front and back of cake. Carefully remove parchment. Gently mark a 1-inch-wide flower bed on each side of gravel path. Mask outer edges of flower beds with parchment. Sprinkle with cookie "dirt." Remove parchment.

For "Grass" Frosting: Transfer 2 cups white buttercream to a bowl. Dip a toothpick into gel paste and swipe through frosting, starting with 4 swipes of leaf-green and 2 swipes of juniper. (Use a fresh toothpick to add more color.) Stir until color is even, adding more gel paste as desired. Transfer to a piping bag fitted with a grass-tip attachment (such as Ateco #133). Holding piping bag at a 90-degree angle, pipe rows to fill both sides of lawn.

For Gum-Paste Fence: Arrange fence pieces off to side of cake in sections for easy assembly. Adhere 2 posts to side of gravel path on both ends of cake, gently pressing into frosting to stick: 2 at edges, and 2 along the long sides. Connect posts with slats: Working with one section at a time, adhere 2 short slats, lining up with edge of post next to gravel path, and gently pressing into frosting to stick.

Whisk together confectioners' sugar, corn syrup, and 3 to 4 teaspoons water in a small bowl until icing is smooth and thick. Dab a small amount of simple icing at end of top slat to adhere to post. (This slat should be set just above grass level of cake.) Repeat on all sides of cake.

Arrange "boxwood shrub" cake balls on either side of gravel path, in flower beds. Arrange "daffodils" over lawn. Hide sunflower-seed "eggs" in grass and around shrubs. Fill small baskets and arrange on gravel path. Decorate with animal figurines.