For over 30 years, I always put my large machinist vice on the left end of the bench and some kind of wood vise in the middle, when needed, like others have shown.
I mounted a medium 4" vice onto a grinder stand like others have shown to take to gun shows, but I don't like it for most other work. I do a lot of work with a large commercial "handy grinder" and like to get my elbows well anchored to control the carbide bits I use. I also prefer to do that when using hand chisels. I find I can't do that well in that type of mount, but maybe that's just me. Grin.
Something I never thought to try, until circumstances dictated it, worked out extremely well. When I moved to the new house, I just couldn't take my behemoth bench I hard mounted into the wall and floor of the old workshop. I had an "L" shaped bench that I originally only intended to be used until I could build another behemoth bench. I had to put the vice on the short leg of the "L" as there wasn't room on the rest of the bench with all the tool boxes I own. This proved to be something I really like. The vice is on the edge of the short leg of the "L" and is about 2 feet from the edge of the rest of the bench. There is about a foot on each side to lay tools and other "stuff." I have no problems getting close to the vice from the front or sides. After using this feature, I'll never go back to the vice on the end of a straight bench. The only thing I don't like about it is there wasn't more long bench on the left side of the vice. So I'm planning on extending the bench to the left of the "vice protrusion" part of the bench, just to be able to lay a long gun resting on that side of the bench as well.