During summer, Varna is relatively well connected with the rest of Europe. There are several flights per day to the capital Sofia (https://air.bg/) and direct flights to some European airports. The direct flights in June can be found also at https://varna-airport.bg/. Apart from this, flights with transfer to Varna offer Austrian Airlines (via Vienna) and Turkish Airlines (via Istanbul).
The conference venue Hotel Cherno More (https://www.chernomorebg.com/), is in the very city center, next to the sea and the beautiful sea park. There is a great variety of hotels and private accommodations nearby.
Varna is a tourist city. The second half of June is on the border of the high season. That is why we advise you to book your trip well in advance.