How do you field strip an Eastern Arms Company Single Shot 16 gauge shotgun?

There may be a screw under the fore end. If so, remove it.

If there is no screw, or once the screw is removed, the fore end should pull away from the barrel, at its front. It may take some effort and may be held in place by spring tension.

Once it comes loose, the barrel can then be opened normally, and will dismount from the receiver pivot.

To reassemble, set the barrel in place, set the fore end against the receiver, and snap it back up against the barrel. Then replace the screw if there is one.