Want to create sessions and slots which we can fetch in GPConnect Appointments Available Slots

As per our use case, we have to sync our customized developed Appointments management system with GPConnect. Which means we have list of staff, they have created their sessions along the slots.

We want to fetch those slots in FREE SLOTS of GPConnect API or what could be the possibility that we submit all data (sessions/slots/appointents) from our system to GPConnect or NHS.