United boss Dennis Greene opted to start with an unfamiliar XI and they were no match for a lively Forest side who led 2-0 at half-time courtesy of goals from Jorge Grant and Sancidino Silva.
Grant and Ilias Polimos added further goals after the break although the Pilgrims improved markedly as more senior players were introduced from the bench, eventually cutting the deficit three minutes from time when Scott Garner steered home Stefan Galinski's shot.
Forest took the lead in the 28th minute when they broke quickly from a Boston corner, with GRANT lobbing the onrushing Sam Vince.
The lead was doubled on the stroke of half-time when SILVA forced the ball home at the back post following Jack Blake's assist from the right.
Two further goals arrived on 55 and 57 minutes respectively when GRANT added his second after being delightfully played in by Silva, who then teed up full-back POLIMOS to finish well from inside the box.
United created a flurry of late chances, with GARNER notably denied on the line by Roger Riera before glancing home Galinski's goalbound shot following a partially-cleared corner.
Boston (4-4-2): Sam Vince (Matt Gledhill 62); Indy Aujla (Zak Mills 62), Conor Marshall (Stefan Galinski 62), Duran Reynolds, Connor Smythe (Carl Piergianni 46); Carlos Djalo (Aaron Cole 46), Jake Hall (Danny Meadows 62), Blake Thompson (Michael Hollingworth 46), Jack Barlow (Kaine Felix 62); Charley Sanders (Scott Garner 46), Dayle Southwell (Jamie McGhee 62).
Forest (4-4-2): Ross Durrant (Aaron Myles 62); Ilias Polimos, Roger Riera, Guillame Asare, Kamal Gutmy; Sancidino Silva, Jack Blake, Manuel Royo (Eddie Schoenecker 62), Derrick Otim (James Demetriou 62); Jorge Grant (Willy Gnahore 62), Tyler Walker (Nikolay Todorov 62).
Referee: Darren Drysdale.
Attendance: 642.
PIC: David Shipman.