I was wondering if anyone in zone 6 has grown figs horizontally along the ground and allowed vertical growing branches to produce figs.   I have been thinking about doing this.  If anyone has tried it has it worked well?  What type of fig would produce well and wouldn't die over winter?  I have Clay Loam soil zone 6a/6b.

Trying that in my newly built greenhouse with 20+ plants - forming all of them to low horizontal shape. Slowly bending branches to create the base structure from which the vertical fruit shoots will emerge.
You can watch the progress here:
http://www.plnazahrada.cz/clanky/projekt-Ficarium-sklenik-plny-fikovniku.php
It's written in Czech but there is Google translate option on that page.
I'm still at the beginning of the project but it is going as expected so far (new figlets already forming on some vertical shoots). I'm going to adjust the techniques on the run if I encounter any problems - for example too dense bushes, etc.

take a look at this
http://figs4funforum.websitetoolbox.com/post/an-overdue-step-over-update-6981430?highlight=step+over&pid=1283576718#post1283576718

But will this method work well in my zone and soil type? Without protection in winter and if not what about as little protection as just raking a few leaves over it? What type of fig(s) would be best for it chicago hardy or are their ones more hardy than it?

I am in the early stages of trying this out.  I planted a handful of fig trees horizontally last summer and buried them with mounds of soil.  All survived but one.  The one that didn't wasn't covered very well. 

However, they are somewhat slow in leafing out this year, compared to the ones I have in pots.  Time will tell whether they are able to ripen a crop.  I also suspect that one reason they are slow in leafing out is that my soil is terrible.  It's dense clay with little organic matter.  My lawn doesn't even grow well.  I hope they adapt to this over time, but I don't know.  I think the roots don't want to penetrate into the clay. 

Even so, once I saw that they survived last winter, which was more like a zone 6 winter with many extended very cold spells, I planted several more this spring.  I looked for trees that had a nice straight vertical trunk, then planted them more or less sideways and bent them down.  They are very close to the ground, maybe only 2 to 4 inches off the ground.  Upside is they will be easy to cover, but downside it's harder to mow around them. 

The best variety to choose for a northern climate, whether in pot or in ground, is an early fruiting one.  So pick a couple early fruiting varieties, and give it a go.  I can guarantee that a few inches of soil provides more insulation than almost anything you can do to protect a traditionally grown tree.