Well, here is the one I have on my Walker Turner drill press. It has two layers of MDF glued togather and screwed from the bottom. I marked and drilled four "T" nut inserts in the lower layer so I could bolt it thru the holes in the table. (I used oak blocks to fill the gap) I then installed T-Track to the top to fit any jigs and routed out the spot for my insert. On the next table, I plan to use a circle jig on the router to make an "off-center" round insert that will allow the insert to be rotated in the table to allow many spots to "mess up".
This table is also edged in imbuia, just because I had some.
Mine is also some MDF layers glued up. I left the center layer free so that it could slide out on both sides for outfeed supports. The waste block piece is dovetailed and can slide out when I need to replace it. I got the hardware from Rockler. I added the drawer to the underside of the table a while after I built the table.