Lidding a hollow form
Ray Carson - Lawrenceville, NJ
Hello Wood Central wood turners. I don't post often and haven't in quite a bit but I have been woodworking. 
I'm currently working on a hollow form which I hope to post pictures of very soon. I'm in the process of making a very shallow or low lid with a finial and have come upon a dilemma of how to hold and turn a piece of wood about 4 1/2" in diameter, about 1 inch thick. I want to make a shoulder for it to sit in the hollow form opening and then have the finial glued into that. I'm a bit perplexed on how to hold the disc without using a four jaw chuck and leaving marks on the portion going into the hollow form. I tried using a four spur center but that was very inefficient. The four jaw chuck I have doesn't expand enough and again, I don't want to leave marks from that chuck.
What can I do?

I live in Hillsborough which can't be more than 20-30 minutes from you.