You could use a pattern bit with a pattern with that size hole. Derek Willis came up with the world's simplest circle cutting jig a few years back. It's in this thread, post #2. https://www.routerforums.com/general-routing/31313-circle-trimming.html You drill a hole in the jig that is the same size as the O.D. of a guide bushing and you just nail it to your template. It might take a few tries to get the diameter right if it's really critical.