The Bible also teaches us how behave, how to live, how to love, how to give, how to forgive, how to ask forgiveness, how to find our way home, how to raise our children, how to pray, who to bind our allegiance to...
The Bible does tell us How God created the world. He spoke it into existence through Jesus Christ - the Word.
For by Him was everything made that was made.
Every time God said, “Let there be...” and there was.
If that’s not specific enough for you, then you and C.S. Lewis are right, the Bible does not teach us How.
It is the specifics we are discussing. Just as God said 'let there be light', but he didn't give us specifics as to what light is. He didn't discuss photons, waves, energy components, etc. If one applied the same lack of specifics, then one would have to determine that light was just made up of God's voice.
The Bible does give us many clues as to how God created the world, unfortunately many people overlook the clues. For example, in Genesis it specifically states over and over: ..and the Earth brought forth.. Seems pretty obvious that God spoke the process into existence but the process he made involved a physical earthly process.