I looked at the site, apart from the ones with obvious segments in them, I think they are just gathered circles. So decide what size you want, take a tape measure and hold it roughly the size, and look at the measurement . That would be the diameter of the circle you need to cut out, but don't forget to add on say another half inch. Rung a strong gather thread around the outside edge, and then fill after pulling up the gathers about half way. Ball everything up in your hand to firm up the filling, then pull the gathers closed and bind off. I hope that makes sense. If you go back to the site, the red cushion on the top row clearly shows some gathers. How you would then add this cushion to the 'pedestal' you have in mind is another matter. Best of luck.