Battle of the Thistles

We didn't take the time to put cardboard under the mulch of my medicinal garden and it's coming back to haunt me... Thistles are popping up all over the place! I saw in a YouTube video from a Michigan gardener that because of thistle's giant root system, you can't just cut them off or pull them out; they'll grow back thicker than before. The trick is to cut them just above the bottom leaves and then cover them with something heavy for three weeks (dandelions are the same way). The plant will put all its energy into staying alive and won't put up new shoots.

In my garden, there are too many to put boards over, although I'm trying. I thought about setting logs down, but the thistles are too big for most of my logs.

Then I remembered I have unused landscape blocks- heavy, decent width. Perfect.

I flipped some upside down because they had cracks in the edges that might let light through. 

Where was my little helper all this time? He wasn't content on a blanket so I tried putting him in the wheelbarrow. He tolerated it for just a few minutes. 😅 I'll keep searching for the magical solution.