Producing another slab of clay I cut a squire slab of clay, which is slightly larger than the vessel rim. While the slab is on a flat surface, cut out the opening for the lid. FYI: I place a piece of plastic on the top of the new slab of clay, then flip it over to cut out the over sized cutout, having the plastic now under the slab, so I can lift it up, after it stiffens a bit (below right).
I remove the center cutout, setting it aside, then lift and lay, using the plastic for support, the slab onto the opening of the vessel, centering the slab and gently pushing down the inside edges, You need to let it stiffen enough( I had let it go all night on a rainy night, uncovered), then I was able to flip this concaved slab over to attach it to the top part of the vessel. (Look in part 2, bottom picture.)
I use the cut out, that I set aside to make the actual lid. I just laid the cut out on another slab of clay, measured out about an inch further on each side and then cut that out. I use the original cut out slab to make the lip on the lid (lower left picture). I make a mark on the cut out about 1/4 to 1/2"in, cutting it out to make a picture frame which I put on the new cutout ( photo below).