Our favorite screwdriver for extracting difficult to remove screws. It has a big handle for a good grip. The screwdriver cannot be too long or it will hit the drip tray and won't fit. This is a Craftsman 5/16" x 1 3/4" slotted screwdriver.

Remove the screen. It may take some prying. If it is really stuck you can use a channel lock pliers.

Remove the small stainless steel diffuser.