Compost bin Q

I've read somewhere that it's essential the bin must be directly on the soil, or it doesn't work??
My problem is horse tail. My current bin is on a double layer of black weed barrier and the mares tail comes straight through it!! Got a couple of 320Lt bins today and am thinking about putting them on a solid base (slabs/concrete). Comments please

As mentioned, should work just fine on concrete - but you might find any liquid runs all over rather than soaking into the ground!

I put some of my bins on concrete slabs mostly to keep the dratted mice out and the persistent weeds out which I couldn't seem to kill. It worked just dandy. As for worms in the compost, a slow cooking pile is fine for worms, not a fast cooking one which might help destroy marestail as well as worms. As for liquid runoff - you can't have everything. That said, you never want so much water in your heap that this happens and turns to sludge.