I came across this table about Summer 2023 slots but since I'm not familiar with these dates, I couldn't understand in which date do airlines publish their Summer season schedule in their websites and to the press (if they have new routes/removed some routes).
IATA will do the the slot allocation for the 2023 summer season during the conference from Nov 15-18.
What the airlines do is mostly independent of that. In actuality, the slots are not completely redistributed but the current slot allocation is slightly tweaked.
The summer schedule for most airlines is readily available right now. For example, in summer Lufthansa operates two flights from Boston to Frankfurt (LH423 and LH421). They have done so for many years in the past and they still do the same for summer 2023. You can book these today.
The IATA slot allocation may results in a few small tweaks to the existing schedule and maybe some new routes pop up. But the vast majority of the schedules are already set and ready to go.
More info on slots: https://simpleflying.com/iata-summer-winter-schedule/