http://scripturetext.com/genesis/1-8.htmBook one of Genesis is just a list of how God Created heaven and Earth in six days (As to these being one day as we understand one day to be, even William Jennings Byran in the Scopes Monkey Trial conceded them to be just steps not days as we use the term days).
AS to the Ancient Hebrews believing the world to be flat, depends on when any book of the Bible was written AND if it was important to the story being told. By the time the Bible, as we know it, was written (Most scholars suggest about the time of the Second temple and the return of the Jews to Judea under the Persians), it was understood that the world was a ball. Some of the books of the Bible use this concept, but most did not for it did not matter to what that books was talking about.
Sir Arthur Conan Doyle, the author of books of Sherlock Holmes, once had Watson till Holmes that the Earth revolved around the sun, Holmes then responds like he never heard of it before. When ask why, Holmes retorted, it did not matter to his investigations if the Earth revolved around the sun, or the sun revolved around the earth. What matter was HOW it affected his investigations and for the detective work he was doing the concept of the Sun revolving around the earth was as practical as the concept of the Earth revolving around the Sun. This was a point Doyle wanted to make with this passage, just because a theory is wrong, does not make it unusable if the results of the using the wrong theory is the same as using the correct theory.
The authors of the books of the bible seems to have understood this concept and did not change the books to reflect that the world was round for if the earth revolved around the Sun, or the Sun revolved around the Earth did not matter in most of the stories of the Bible.