Have you considered planting them in a raised bed or mound? I also have clay soil, and that method has worked very well for my figs (as well as a number of other fruits).

I second shazaam's suggestion.

We also have heavy clay soil. Figs do great in it when I plant them in raised beds or high and throw a lot of compost and straw around them so that they are in a mound. Also, mulch heavily (again...I use straw) The mulch will break down over time and add nutrients to the soil. It will also help the clay soil remain moist, so it doesn't bake into adobe/concrete in the summer heat.

Also...you might want to wait untill all chance of frost is past before putting them in ground. They're kind of sensitive for a couple month after being transplanted.

SHAZAAM has a good idea I use raised beds too.