The Pilgrims were 4-0 victors over Gresley FC at the Moat Ground following goals from Pratt in the 25th, 47th and 63rd minutes.
Jack Withers had earlier headed United into a seventh minute lead.
Boston (4-2-3-1): Seth Greeves; Leighton Boughen, Taylor Gray, Jack Withers, Jack Brown; Callum Rodger, Jamie Gaukroger; Marshall Young (Depierro Mpeya 75), Jenson Bark (Jenson Ball 75), Xander Crashley; Ryan Pratt (Arek Michalczyk 64). Subs (not used): Leon Thornton, Oliver Swaby (gk).