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HELP: Website that allows users to personalize product for purchase?

Hi there,
I’m trying to make a website similar to where customers can personalize (edit name & cartoon) their product before ordering.

Hooray Heroes offers books with varying personalized stories, my product isn’t a book and wouldn’t offer stories. My products are actually mom-merch phone cases showcasing text and a cartoon of parent and child.

I would love the website to be as identical as possible in function to that of Hooray Heroes’ where you enter a name, choose skin color, hair, special features etc, and it shows a preview.

I have no clue where to start. Help!

Here is my site Read-Only: LINK
(how to share your site Read-Only link)