The Pilgrims triumphed 2-0 at Hereford FC courtesy of Clare's 33rd minute breakthrough and Abbott's 76th minute penalty.
The result wrapped up the Pilgrims' fifth league double of the season and ensured they secured a top half finish with 58 points to their credit.
United were ravaged by unavailabilities and even lost the services of centre-half Ryan Cresswell in the warm-up to leave just three players on the bench including reserve goalkeeper Dylan Parkin and youth team defender Taylor Gray.
The game, played against the backdrop of a blustery wind, failed to yield a clear-cut chance before the half-hour mark. When United’s opportunity arrived, Andi Thanoj saw his long-range drive tipped wide by Matt Yates and from the resulting Nicky Wroe corner, CLARE slotted home from close-range.
Hereford had a couple of chances before the break, with Rowan Liburd’s header blocked by his own team-mate Jordan Cullinane-Liburd, before George Willis thwarted Tom Owen-Evans.
Clare blazed wide six minutes into the second half and Hereford enjoyed a strong spell thereafter, with Ryan Qualter bravely denying Liburd, before the big Bulls striker hooked an effort over the bar following Owen-Evans’ cutback.
Willis made good save to keep out Tommy O’Sullivan and, notably, substitute James Waite.
United sealed their win with 14 minutes to play when Josh Gowling tripped Qualter and ABBOTT sailed home the resulting spot-kick in the absence of regular taker Ben Davies.
Gray was handed his National League North debut in stoppage time as the Pilgrims concluded the campaign on a winning note.
Hereford (4-1-2-1-2): Matt Yates; Jak Hickman (Theo Wharton 46), Jordan Cullinane-Liburd, Josh Gowling, Danny Greenslade; Keiran Thomas; Tommy O’Sullivan, Tom Owen-Evans; Elliot Richards (Kyle Finn 72); Rowan Liburd, Mike Symons (James Waite 46). Subs (not used): Louis Ezewele, James Wesolowski.
Boston (4-3-3): George Willis; Cameron Hawkes (Andre Johnson 83), Ben Middleton, Ryan Qualter, Ashley Jackson; Brad Abbott, Nicky Wroe, Andi Thanoj; Jay Rollins, Tom Clare (Taylor Gray 90), George Smith. Sub (not used): Dylan Parkin (gk).
Referee: Ben Speedie.
Attendance: 2,232 (71 visitors).