Here is the treasure map for this DLC. Hope it helps :)
EDIT: Added 3 vids for confusing/hard boards
EDIT: There is one board underneath the byron bay iconEDIT: Multiple people in comments have had boards not count if that happends quit the game and relaunch it and you should be able to smash it againEDIT: Glitch might be caused if you have a skill chain while hitting a boardImage#1(Bottom left on map):
Image#2(top of map):
Middle one on Tidal Teeth(left side of picture) is below the track
Image#3(Bottom Right of map):
Video#1 (Not really hard one but might be a bit confusing to some so thought i would add it):
Video#2 (this one is below the hotwheels track):
Video#3 (hidden in cave):