This achievement related to the 2nd mission "Hangar 18 1/2" of this DLC.
This achievement is MISSABLE!! Make sure to have a save before every mission of this DLC.
Just in case you missed these clipboard or other achievements of this DLC:
1/ Load your previous saved game see if it's before the mission.
2/ Find a buddy who have the save before this mission and/or notfinished this mission yet.. Ask to co-op w/ him/her.
3/ Update: After the last DLC released, as the development team stated you can replay these DLC mission anytime by choosing it on your cell phone now. (But still need to start from the 1st mission.)
As Twitter change the screenshots' links for a long time ago.. Guess I better change the photo host. Here's the link to my Flickr Album: https://flic.kr/s/aHskyCqFdW
There are 2 hidden clapboards in each set. The set means that the place before/after the combat scene. So there are total 3 sets you can find these collectables.
The 1st set:
1/ Just in front of the crushed plane.
2/ Right after you go up to the roof.
The 2nd set:
3/ After you exit the scene, there's a bed room set right in front of you. Go to the bed and turn left and you will see it.
4/ This is the tricky one, I miss it at the 1st time.. When they talk about Prof. Genki you will see a wrestling ring with 2 huge box & a sofa. The clapboard is behind the box with a big pink question mark. Press jump to enter the ring to take it.
The 3rd set:
5/ After you run out of the scene and you will see some replacement of your homie. Go further, you will see a place look like Zimo's crib, the clapboard is in the kitchen.
P.S. Just forgot to take a photo first. But the one should be here in the corner.
6/ After you take the 5th clapboard, turn right and you will see a huge robot, the last one is just behind it.
P.S. See the light between the robot's legs? Okay, my camera sucks.
I took photos for these clapboards.
Will upload when I finished the other missions ;)
EDIT: Photos added. Please give me a reason if you vote thumbs down.