Irrespective of whether one believes in Gap theory or not we see that the word Bara and asa is used several times in Genesis interchangeably. What confuses me is how are we to understand the actual meaning of the word in the text. Eg. in Genesis 1:7 we have the word yaas, are we to understand that it means to create out of nothing or to form or shape something?
On the following link, go down to the item marked, God's Day One Creation - A Type of the Word of God.
The first four and one-half pages provide much information you desire. A great example on Day-Six shows that man was created (bara') as one complex spirit having two operative capacities, male and female, and named Adam--not Adam and Eve. However, later on that same day, that same Adam was formed (yatsar) as flesh and blood and made ('asah) a living soul--still male and female. Even later that same day, Eve was formed (yatsar) out of the rib of Adam as a new and distinctly separate being. She was given the operative capacity (spirit) of the female, then, and only then was she joined back together with man to accomplish many things, including to provide the means for God to Father a Son--the seed of the woman--that perfect Lamb of God--that eternal King-of-Kings son of Abraham, Isaac, Jacob, Judah, and David.
The root idea of bara seems to be "purify". blueletterbible.org/lang/lexicon/lexicon.cfm?strongs=H1252
All of Genesis is about purification. The waters were mixed with the dirt. God drew the waters to one place. God "purified" the waters. And its not just about elements. Animals too are purified. (Think "purebred"). God created apes (creepers) and then drew out man from the apes. God purified the human race by making us rational.
This short study shows that there is no basis for saying that bara only means an instantaneous, out-of-nothing, supernatural creative action but that asah only means a slow, out-of-existing-material, natural process of making (under God’s providence, of course). In the creation account (Genesis 1:1-2:3) both words are used in reference to ex nihilo creation events and both are also used in reference to things God made from previously created material.
So, only the context in which the words are used can give the precise meaning, if there is a distinction to be made. The context of Genesis, indeed the whole Bible, is overwhelmingly in favor of interpreting both bara and asah in Genesis 1 as virtually instantaneous acts. Whether God created something out of nothing or created something from material that He had just made, the force of the words in context is that both kinds of activities were instantaneous and supernatural after God spoke “Let there be . . . .” In Genesis 1 and 2 we should assume ex nihilo (out of nothing) creation unless the text clearly indicates otherwise (e.g., Genesis 2:7, 22).
We can apply this to
Darby Bible Translation Genesis 1:7
And God made [asah] the expanse, and divided between the waters that are under the expanse and the waters that are above the expanse; and it was so.
From preexisting waters, God separated them into two parts: lower waters and upper waters.
8 And God called the expanse Heavens. And there was evening, and there was morning -- a second day.
I'm fine with this interpretation. Hope this help.