We are doing a minor reno of our kitchen. The site-built cabinets are in pretty good condition (the drawers stick a bit but work, the doors are solid) for original 1964 cabs. The problem is that we need to replace our wall oven, which is currently a 24" double gas oven. We would like to replace the oven box so that we can fit a 27" single oven/mw combo. To do this, we need to build a new wall oven box.

Can anyone point me in the direction of detailed instructions for building a 27" wall oven cabinet? We've built furniture before, but always with a pattern. Thanks.