If I reached the video from the recommendations on another video/the YT homepage, I'll go back and select "Not interested" there. It's not foolproof, especially

If I reached the video from the recommendations on another video/the YT homepage, I'll go back and select "Not interested" there. It's not foolproof, especially b/c the back button will still cause YouTube to update the original page (and so the previous recommendation can disappear entirely), but anecdotally this strategy seems to work pretty well.