To make bottom cookie: simply take cookie cutter apart by squeezing the fluted edge and releasing. This will give you a fluted cookie cutter to make the base/bottom cookie.

To make the top cookie: replace the fluted cutter, so that the entire linzer cutter unit is one-piece, as it was before you started. Press down on the dough with the cutter, raise cutter slightly, then over your cookie sheet, press the injector. The result should be a cookie with a fluted edge and a shaped center.