I didn't take any more pictures, but there was not a whole lot to the process.
There is about a 1 1/2" lip all the way around this opening, that is what the off-cut I purchased is sitting on. Monaco glued a 2X2 to the bottom of that lip and used screws to secure the propane stove top. I'm thinking of adding 3/4" plywood under the new insert to raise the stove top a little as the handle of our frying pan barely clears the counter top.
I'm not sure what brand this counter top is and I didn't think to ask when I found the off-cut, but it works just like engineered wood like particle board or MDF. It doesn't chip out when drilling or cutting.
I had to enlarge the width of the existing hole in the counter top by about 1/8" on each side to take the stove top. I used a Bosch trim router and a 1/4" straight bit. The base plate on the router and the diameter of the bit lined up to take just enough off of each side without having to use any guide except the flat wall of the opening. I just butted the plate up against the side of the opening. You can use a different size bit to take off more or less material.
I drilled a 1/2" hole in each corner of the hole marked out on the off-cut, then used a jig saw to cut out the hole. A sharp blade makes quick work of the job. This stuff is a dream to machine, cuts fast and doesn't splinter or chip.