Better wait and plant it in the ground during your spring time. For storage using the cinder block shed will be Ok. It may not be colder than the the one on the slab. For added protection during the first year, cover your plant with a couple of layers of burlap, after shedding leaves, including the pot. Do it after temperature gets to freezing. Bring it out in the spring and plant it when the ground warms up.

You have to watch and make sure that the soil stay moist and not dried during the storage period. Make sure temperatuires in storage are don't drop more than a couple of degrees below freezing.

I purchased and planted a Chicago fig last fall to replace one I removed from along my house foundation. I was concerned about its winter survival since I was placing it in a very open area that did not provide any protection from drying northwest winter winds. Fortunately, there was a fig article in a gardening magazine about the same time that said to wrap burlap around the fig and fill it with dry leaves for over wintering. So that is what I did--drove four tall stakes in the ground, wrapped the burlap around it, and filled it with leaves. However, I did find out that after a rainfall, the leaves significantly compacted down such that I had to add more to fully cover the plant.

I was concerned in the spring that it did not survive as I saw no new growth shooting up from the ground. (My original fig always died back each year and then put up new growth in late spring.) However, when I scratch checked the actual stems, they were still green and did not die off. The Chicago fig is one that awakens very late from the winter and with the late spring we had this year, it was even later. I will do the same process this year for overwintering while it is still small. One thing I did do when I planted it last fall was to water in a root stimulating fertilizer called Roots to help encourage root development until the ground froze. If you decide to plant your fig vice keeping it in the pot, I would recommend doing this.

You can make a small fence around it from chicken wire and fill it with leaves and pine needles. Just make sure to have extra leaves on hand to top it off as they break down. You will be enriching your soil and giving your tree lots of time to keep growing new roots through the winter. It will be significantly ahead of a tree potted then planted in the spring.