After leaving Hoth, the Rebel Alliance rendezvoused at Sullust.
ON THE EDGE OF THE GALAXY, many parsecs from any Imperial star system, the rebel fleet has gathered near the planet Sullust.
They’ve given up on maintaining a base on land. This is all that’s left, a handful of strange, patched-together starships, a few partial squadrons of fighters, and, of course, the Millennium Falcon.
All the pilots have assembled on the flagship to hear from Mon Mothma, the brave leader of the Rebel Alliance.
Return of the Jedi: Beware the Power of the Dark Side!
Note that the Emperor was well aware of this but chose not to engage them, preferring for them to come into his ambush rather than scatter again.
VADER: What of the reports of the Rebel fleet massing near Sullust?
EMPEROR: It is of no concern. Soon the Rebellion will be crushed and young Skywalker will be one of us! Your work here is finished, my
friend. Go out to the command ship and await my orders.
Return of the Jedi: Script