I did a cake similar to this. It is in my gallery. It started as a half sheet and then spur of the moment i cut and stacked levels. I tinted buttercream the color of the soil /dirt /ground, iced the sides and pulled a pastry comb in a zig zag motion through the buttercream. I was surprised at how well it worked. Super easy! Then i used a grass / fur tip and did the grass
Psalm 127:1 Unless the LORD builds the house, the builders labor in vain.