les poches des hommes. We change the les hommes to des hommes. Is there any instance where we use 'les' after 'les'?
Des is a contraction, so where you might think it should be "de les" you always use des. Similarly where you might expect it to be "de le" you always use du. If you wrote les poches, les hommes it would change the meaning to "the pockets, the men" which is grammatically okay if you are making a list.