Please tell me why you negative voted because currently, this is the only guide that has explained what full distraction is, no offense (I will change the wording if you can't understand).
Repeat 24 more times across your vacation on Rook Island. It'd help if you marked your enemies before attempting to distract them first because you can analyse what they are doing, as well as know when they have completed their survey and started to return to their original patrol route. You must then allow them to look around and return to where they were before the distraction was created, and once they do, it'll count as a 'full distract'.
To fully distract enemies with rocks, one must throw it nearby them and allow them to investigate the location of where the rock landed.