BlueBuildercreate:  
  type: assignment  
  actions:  
    on assignment:  
    - flag npc "select:0" 
    - define cuboid cu@<npc.location.x.sub[15]>,0,<npc.location.z.sub[15]>,<npc.location.world.name>|<npc.location.x.add[15]>,10,<npc.location.z.add[15]>,<npc.location.world.name>
    - walk <def[cuboid].get_blocks[GRAVEL].random.as_location>