I would till some sand into the clay which is gonna increase drainage.

EG

Well, I'm not actually planting in the clay, know what I mean? Just trying to get it to be eventually useful. The soil forum lasagna gardeners layer newspaper and coffee grounds on top of existing weeds. I was wondering whether something like that would work over clay and below my raised bed soil.

You need to incorporate your mix into the clay, else you won't get drainage. Then you will be unhappy.

And avoid adding sand to clay as it may aid in cementation, esp in the PedOCal region. Just work the mix in well to the clay a shovel deep.

Dan

You can make the clay immediately useful by mixing it with your soil. My raised beds consist of my native clay, vermiculite, peat, and compost, all mixed together. I level my beds, put down wire, then brown paper bags (or newspaper or cardboard) and then apply a mix of the above ingredients. It works well.

I would not add sand. We were planting a tree in our swingset area which has a lot of sand and the clay in that area was nasty. I could not imagine trying to coax health from my veggies in that.

Mixing the sand with the clay would be a danger of making bricks, yes. If money would allow certainly remove the clay and bring in topsoil mixed with compost. Years back when I made raised beds at our old home I did the French double digging and incorporated sand, compost and topsoil back in with the clay we found deeper down. Best garden I ever had. :)