As a complete novice to any power tool more sophisticated than a sander, I thought I'd share my experience making a ZCI for my TS3650 with others, on the basis that if I can do it anyone can.
I cut a strip the width of the standard insert off the long edge of a 2' x 4' peice of 1/2" in MDF on the saw. This gave me enough to make 3 inserts with about 5" of waste left over.
Carpet taped a piece to the original plate and shaped on my router table. I checked, double-checked and triple-checked the set up as I can only imagine what would happen if a router bit hit metal. Besides which, the router table scares me just to turn it on!
Anyway got the MDF to size then went to cut the slot on the saw table with a block over the insert for safety.
As others have mentioned, you can't lower the blade on the saw far enough for the insert to completely settle into place at first so it goes perhaps halfway down and rests on the blade, which then has to cut space for itself.
Well, time after time I got everything ready and switched on the TS only for the circuit breakers to immediately trip. This happened so fast that the blade never made so much as a pinprick impression on the MDF, much less start a cut.
In the end, I went to the back of the saw, held the ZCI down with my left hand and moved the drive belt with my right hand to manually turn the blade. I cut deep enough that the ZCI would go all the way into the slot.
I'm not saying it was hard work, but I will be checking my next DWP bill for a small credit as I'm sure I must have been returning power to the grid...
Final step was to rout about 1/16" of the bottom edge of the plate to let it sit fully into the slot.
Then fix it down, turn on and raise the blade the rest of the way through the ZCI and I was all done...