• Bake 2 yellow sheet cakes (Dimensions: 9x13), 2 chocolate sheet cakes (Dimensions: 9x13) and 1 cotton candy dome cake (5 inch diameter). Please note you will have leftover cotton candy cake batter than you can use to make cupcakes for another project of your choice.
• Keep these cakes aside to cool completely.
• While those are baking and cooling, prepare the yellow buttercream frosting.

Cap cake

• Let's make the cap cake first. Place the dome cake on a cake board that's the same size as your cake. Frost it smoothly in buttercream. Chill it for 20 minutes in the refrigerator. Roll out black fondant and spread it over this chilled cake. Smooth it out with a fondant smoother. Cut excess along the base of the cake with a pizza cutter. Push a bubble tea straw in the center. Keep aside.
• Make the top portion of the cap by cutting out a square piece of cardboard, using scissors. Use a black edible marker to color the edges so that if your black fondant doesn't entirely cover the sides, the cardboard won't show through. Spread a thin layer of icing on top and spread black fondant. Cut excess along the sides with a pizza cutter or knife.
• For the final touches of this cap, use a small circle cutter to cut out a small circular piece. Brush some corn syrup at the center of the square cardboard piece. Fold a ribbon in half and stick it here and then place the circle fondant piece on top. Press gently until it all sticks into place. 
• Stick this prepared square cardboard piece on top of the dome cake with melted chocolate or thick royal icing. Steam everything to get rid of the powdered sugar residue.

Edible diploma

• Roll rice krispie treats in a long cylinder shape. Spread buttercream along the sides.
• Place this iced rice krispie treat log on rolled out white fondant. Roll from one end to the other end until the sides are covered. Cut excess with a sharp knife.
• Cut out 2 white fondant circles, using a cookie cutter and stick those on the top and bottom of the log with buttercream icing. Wrap a red ribbon around this diploma.

Assembling

• Place the 2 chocolate sheet cakes side by side on a large rectangle cake board. Spread icing on top. Place the other 2 yellow sheet cakes on top of the icing. Spread icing smoothly on the top and sides of the cake.
• Fill a piping bag with yellow icing and attach the large star tip (Wilton tip 1M) and pipe roses along the sides of the cake as well as the top of the cake. If you have never done this, check out this post on How to Pipe Red Rose Cupcakes where I share detailed instructions.
• Decide where you want to place the diploma and the cap on this sheet cake. Add dowels or bubble tea straws in those spots for support. Place those prepared pieces on the cake.
• To fill up space on the cake board, cut out the letters for "Congratulations Class of 2024" using cookie cutters. Stick them on the cake board with buttercream icing. Enjoy.