Not a Norway maple but I have cut through the root web of a maple tree and planted both herbaceous and tree peonies under it. It would be better to plant at a greater distance than 3-6 feet because the branches could keep the plants from getting enough moisture except in a very wet season.

Dig down through the root web to see how deep the root webbing goes. If you would put a pot or other barrier deeper than that you could retard the root growth in that area.

A herbaceous really like more sun than provided by a maple. Mine has grown and flowered but not sent up many stems. Bulbs of all kinds would do better.

I agree with the previous post. If you are going to try it, plant the peony out further than 3-6 feet. They aren't fond of root competition. Also, I wouldn't recommend sinking in a clay pot unless it is at least 3 feet in diameter. Peony roots like to branch and spread out as opposed to go down deep in the soil. Keeping them retained by a sunken pot or another barrier would make for a weak plant. Best of luck!