Gatsby 5 introduced the Slice API to enhance the efficiency of updating common components across a website by allowing these components to be built separately and then integrated into existing pages. This approach, however, restricts the use of non-serializable props, such as functions, which cannot be reliably serialized for high-precision incremental builds due to their non-primitive nature. To work around this limitation, developers are encouraged to use React's Context API to provide and consume functions within slices rather than passing them as props. This method ensures a better developer experience by maintaining the integrity and precision of builds. Despite the restriction, the Slice API offers significant speed advantages during site-wide updates, making it a valuable tool for developers. Paul Scanlon shares insights and a practical example of implementing a theme toggle using this approach, emphasizing the benefits of adapting to the Slice API's design for optimal performance.