Clash,
You asked: Do you start with scriptures alone (sola scriptora) as the authority?
As I mentioned earlier, I believe Christians should read the Bible with the help of the Holy Spirit, and then decide for themselves what they believe the Bible is saying. (I John 2:27) This approach is more than the scriptures alone.
So far as your saying that a "scriptures alone" approach would require us to understand that when Genesis says that God created the world in six days that it must mean "six literal (24 hour) days," I believe you are in error. For if such were the case we would also have to believe that God created the heavens and the earth in only one day. For Genesis 2:4 speaks of "the day that the Lord God made the earth and the heavens." Now, which is it? Did God do it all in six days or in one day? There is no contradiction here for the reasonable person. The writer of Genesis obviously used the word "day" as we often do, to refer to a larger period of time. As in, "In my father's day things were done differently." The six days (or periods of time) in which God created our world, when spoken of together, can be referred to as one day (or period of time).
So far as "man's assertions" go, I pay them little attention. I do, however, listen to God's Holy Spirit and use the common sense God gave me. And I believe the Holy Spirit has often reminded me that the Bible contains much non-literal language. The Book of Revelation comes to mind. So do Jesus' words that we must eat his flesh and drink his blood to gain life. God expects the reader of scripture to use their discernment in determining when we should understand the scriptures in the simplest, most literal way and when we should understand the scriptures in a deeper, less literal, way.
God gave us good minds and the ability to reason. I'm sure He expects us to use them both when we are studying His word.