Fit a plain, fabric lampshade over the top of the lamp. The shade should be slightly larger than you want the finished shade, so stand back a few steps to see how the shade fits. If it looks just right without the alterations, pick a shade two or three inches in diameter larger for a properly fitted corset shade.
Lay an unused corset on the table, and lace the back of the corset. Leave the laces loose to allow for adjustment after the corset is fitted over the lampshade.
Set the lampshade on the table, and then wrap the corset around the shade. Secure the top two or three clips on the front of the corset to make sure it fits well around the lampshade. It should fit snugly, but not so tight that you can’t fasten the entire corset. Remove the corset after the initial fitting.
Heat up the glue gun. Coat the exterior surface of the lampshade with hot glue. Wrap the corset around the shade again. Fasten the clips down the front of the corset, and pull the strings tight. As you pull the strings tight, the lampshade will take on the classic corset hourglass shape.
Let the lampshade dry overnight. Check the top and bottom of the lampshade, adding more glue as necessary for a tight bond between shade and corset.