Short answer
Flores and Corvo are accessible mainly by air, with limited boat connections. SATA Azores Airlines operates flights from other islands, but schedules can be sparse and weather-dependent. Boat trips between the two islands exist but are infrequent and subject to sea conditions. Always check official SATA and local ferry operator websites for current timetables and book well in advance, especially in summer.
General information, not legal or tax advice. Rules and amounts change: confirm with official sources.