We have also made the panels for the dinette seat cushions. These are try-cell panels glued to the right curve in place and fit with just the right amount of clearance for the upholstery. Then the edges are routed out and packed with thickened epoxy. Then they are coated with epoxy and sent off to be upholstered in really nice soft leather.
This is what it looks like when were done. You have to have a very smooth work surface for this as you need to sand both sides with a hard block and any bumps in your table can quickly result in a hole.
As seen below the result is very nice. The seam is all but invisible and smooth to the touch.