Plans for the Bomber County Gateway Memorial, which is near the Nottinghamshire border, were announced in 2018 to mark the centenary of the RAF.
Each wing measures 14.5m (nearly 50ft), and the sculpture is tilted to give the impression that the Lancaster is in flight.
The trust’s Charlie White said the final stages of work involved laying 3,000 sq m of turf, which had been donated by a local firm.
He said it would enable visitors to view the sculpture up close and enjoy “the hard work of the last eight years”.
Lincolnshire is known as Bomber County due to the large number of military airfields it had during World War Two.