I use cardboard boxes cut open and laid down flat on the ground and then lay weed cloth over that and then wood mulch as the final touch for my paths. Seems to work well except where 2 pieces of cardboard meet if I don't overlap them. Weed seeds DO however grow on TOP in the mulch. Weeds are tough and many can grow in just about ANY kind of situation. I find my biggest problem is the seeds blowing around and landing in areas I want to keep weed free and then sprouting. For those, I just do regular pulling before the roots get too deep to actually get out.
