1. Assess the current backend, storefront requirements and any systems that need to integrate.
  2. Design the API contract and the backend changes needed to support a decoupled frontend.
  3. Build the frontend application and connect it to the backend APIs.
  4. Test performance and functionality under realistic traffic.
  5. Deploy, with a support window afterward to handle issues.

Timeline and scope depend on the size of the existing store and the integrations involved — request a quote for a project-specific estimate.