Ask HN: How do you teach problem solving skills to software engineers?

More often than not, I get people who have decent work experience and seem suited for a role but fail to unlearn and re-learn new ways of doing things. A lot of these people tend to come from a service company background where they do not dive deep into solving problems with code and instead try to cut-paste from across the internet which is good enough for projects that might not ever get completed or used only internally.

How does one re-train people who might have learnt computer science fundamentals at some point but have lost track of how to solve problems over the course of their earlier work experience?