I like a fixture plate made with a grid of tapped holes with 1" centers. I find it's most versatile as it allows all kinds of fixtures and sub-fixtures or vices to be held. Can use dowels for stops and to push against using low-level clamps like Mitee bite, even on odd-shaped parts. You can bolt down strips of material and machine soft jaws which can then push against.

It can use standard fixture clamps with a lot more scope for finding a place to hold because you are not restricted to slots. Holding parts for full uninterrupted profile passes is easier because you can often all ways find a hole to bolt part down with which you can't always land on a slot.

You can hang it over the edge of the table and take full advantage of all the available travel with Clamps effectively outside the travel area. For instance, a 4th axis can be hung on the end and not rob any tablespace.