Does Genesis One Teach Creation Ex Nihilo?

A lot depends on what you mean by the word "teach" here. I don't think that Genesis 1:1, "In the beginning God created the heavens and the Earth," asserts explicitly "out of nothing." It doesn't explicitly say, “In the beginning God created the heavens and the Earth out of nothing,” right? But I think it implies it; it is a logical entailment of his creating the heavens and the Earth because the heavens and the Earth is everything that there is physically, and therefore there could not have been some sort of primordial matter or stuff out of which God formed the world. So I would say that creatio ex nihilo is an entailment of Genesis 1:1. Now, if you take the teaching of Scripture to include not only what it explicitly asserts but also what it entails, then I would say, yes, Genesis 1:1 teaches creatio ex nihilo even if it doesn't explicitly assert it. And I think this is confirmed by several other passages in both the Old and the New Testament.