Good you found a way to make your approach work, but you are massively over complicating what you are trying to do, i.e. adding html into a Coder and then placing that inside a Container and then inside another developers free stack all because you are trying to just centre some icons
I made a whole series of tutorials of which the first would be relevent to what you are doing.
Positing content inside things and on the page is what Sourcedoes best, so spending some time on Source turorials will be time well spent.