There are many design options, and the choices are largely personal.
When I built my last table top, I elected to go with a "precision", heavy-duty "base" for the split fence - 3"x3" 3/8" thick aluminum angle from Online Metal Store | Small Quantity Metal Orders | Metal Cutting, Sales & Shipping | Buy Steel, Aluminum, Copper, Brass, Stainless | Metal Product Guides at OnlineMetals.com
. The three-inch size left plenty of material to retain stability, and provides higher support for the fence faces. I also elected to cut T-slots
rather than installing T-track, since I felt the latter consumed too much of the thickness of the MDF fence face pieces.
For the bit-clearance area, I drilled corner holes and then used my Porta-band saw for the side cuts and a jig saw for the top and back cuts. The slots for the lateral adjustment T-bolts were carefully routed with a spiral carbide up-cut bit. I routed a dado for the T-bolts, so they would be "captured" prior to laminating the two layers of the top.
I also elected to use a combo track (t-track and miter slot) in front of the router, located such that my feather boards would reach.
For me, the key design elements were:
1. precision and stability of the 90° fence-to-table fit,
2. the ability to use feather boards on both the fence and table,
3. split fence for a variety of bit types.
I may go back and add tongue-groove cuts on the center edges of the fence faces to allow insert sections, but so far haven't seen the need.