Honestly, I like Roundup. Black plastic works but you have to weight it down and it tends to blow around when you are putting it down. And then it can disintegrate partially and be a real bugger to clean up. And ...also...if you live in the south you are building fire ant havens. They love to get under anything.
Dirt tends to pack under plastic. If you buy concentrated roundup...like 40% it isn't very expensive if you buy off brands. Just don't spray once you plant.
I am not an organic gardener...
X2 I got old enough that I had to quit some of the hard stuff . Roundup and preen are good tools . To each his own .