Well, that got me a little further. Thanks, Bill.
I found the exploded view of the parts diagrams on
OEM Replacement parts for Tools, Appliances, Consumer Electronics and more | eReplacement Parts and the table insert appears to be the same shape as the one in my Unisaw, although likely not the same dimensions, so you should be able to copy the shape of the original metal insert the same way that I do mine, however, I can't see how the insert level is adjusted in the assembly drawing. I have set screws in mine that push down on tabs below the table but sticking out into the insert opening. If you have these tabs, the set screws in your wooden insert will need to be located above these so the set screws push down against them to lift the insert to the level of the top of the saw. With set screws threaded into holes in the insert, you will be able to adjust them from above with an Allen wrench, to bring the insert level with the table of your saw and not rocking- all 4 set screws need to be adjusted for a level insert that doesn't rock.
I can't see it in the drawing, but your metal insert must have some kind of pin sticking out of the back edge of it This pin or tab will keep the back end of the insert from lifting if the saw blade should catch on it. It's a safety feature, so you should figure out how to duplicate it's function on your wooden inserts, even if it's appearance isn't the same. Your method might be like mine, a roll pin driven into a drilled hole in the back edge of the insert that catches in a little recess in the back end of the hole that the insert fits into in the saw table.
Once you have the insert cut out and sanded to fit, plus added the set screws and pin in the back edge you will need to cut a blade slot in it. My Unisaw blade doesn't go low enough to be able to install an uncut insert with the 10 inch blade on it, so I use a 7 1/2 or 8" blade to make the first cut. After installing the blade with it in it's full down position, install the blank insert and level it with the top surface of the saw table. using the set screws. Then place your fence over it, but to the side of where the blade will be. You will be using the fence to hold the insert in place whil you raise the spinning blade up through it. Make certain that you have positioned the fence to the side of where the blade will be cutting.
Start the saw and slowly raise the blade up through the insert until you reach the highest blade height that you will want the saw to reach. In my case, I then replace the smaller blade with the 10 inch blade that I will be using with the insert and then repeat the process to cut the blade slot for that blade. Now you can move the fence away and set the saw up for your first cut with the zero clearance insert and the blade of choice.
I always make a bunch of zero clearance inserts at the same time and then keep them without saw cuts until I need one. I have an insert for each blade and if I cut 45's with that blade, then I have another one for doing that. The blade information is written on the under side of the insert, so I don't use it with the wrong blade. They are all a little bit different, so each blade needs it's own zero clearance insert. Zero clearance inserts wear out. By keeping extra blank inserts available, It's quite easy to cut one and replace the worn insert quickly. I make more when I'm down to two or three blanks.
Best I can do without seeing a better picture of your insert and it's hole in the saw's table top. If you have problems, try to post photos showing where you are having the problem.
Charley