If you are using 1 /2" for the router insert, it would be easier to use a piece of 1/2" for the top and then a backer of 3/4" under. That way the insert would sit almost flush with the laminate top. No routing out for the insert required this way. Just make the opening in the bottom 3/4 " piece about 3/8" or 1/2" smaller all the way around than the top 1/2" piece, like a shelf. Another suggestion is to use a premade table insert just for that router from http://www.ptreeusa.com/routerPlates.htm
Scroll down to see all available. The inserts for the plate are hard to duplicate by hand and you don't want to be dismounting your router to fit a different size opening all the time either. These discs just turn in and out 90 degrees.
Router tables are available for $180.00
Question: I use a Mast R Lift with the PC 3 Hp router which I purchased with the motor only. So, I don't know how thick the base plate that comes with the router is, 1/4" maybe? Seems like you are going to lose some cutting depth due to the stack of base plate, and 1/2" insert. And unless you come up with a quick detach system for changing the router from insert to insert this will be a PITA. That's another reason why I'm suggesting use one insert, with interchangeable center discs, to expedite bit changes.
It's interesting how this post has evolved from "How to build a door" to building a router table to build a door. BTW, I absolutely wouldn't be without the lift, or some above the table top kind of height adjustment. The crank on the Mast R Lift has a dial indicator built in and it's a breeze to change heights in small amounts. All these features can be found on a shaper, of course, but in this case it's a little late for that now.