Fruitnut grows grapes in pots with success, maybe search back for his posts. Clay soil is okay for grapes just mound or raise the crown up a foot or so. They will do better in the ground.

Thank you, the first foot of digging is not bad but after that it's so bad even a shovel won't do it

You don't have to dig more than a foot deep.

As was said, the grape will do better in the ground.

And that heavy clay will provide numerous free fertilizer elements and will hold water a long time.

Dig your hole, then mound the soil as was suggested to keep the crown above any standing water.

Grapes in containers is a novelty. I just got a reliance and am keeping it in a container. But I, and you, shouldn't have high expectations.