Level the two 8-inch rounds and stack with 1 cup buttercream; chill 15 minutes.
Crumb-coat the stacked cake with 1 cup buttercream; chill 20 minutes.
Tint remaining buttercream blue and lightly texture with an offset spatula for sky effect.
Attach foam ball or half-sphere to cake top with a dab of buttercream; secure using two skewers pushed into cake.
Roll gum paste into a small basket shape and let dry 1–2 hours; if using candy, skip drying.
Insert four skewers into cake around sphere, trim to same height, and drape a thin gum-paste “net” or piped icing between skewers.
Place basket on board, attach to skewers with extra buttercream, and add candies or cloud piping around base.