[Odoo 19] How to develop multiple websites in odoo using website module via code

I want to develop two completely custom websites using odoo website module from scratch within a single Odoo database. For both websites, I do not want to use Odoo’s default website design or themes instead, I plan to implement my own custom designs.

I’m looking for guidance on the best approach to achieve this. Specifically:

1. How can we implement this, because by default when we create websites, we get odoo default themes and pages. We want to build our own?
2. Is there any reference repo or project which i can use as reference?
3. What is the recommended or best practice in Odoo for handling multiple fully customized websites in one database?

In short, I would really appreciate guidance on the most scalable and maintainable approach for this scenario.