The game a Bloomfield Road ebbed and flowed pleasingly during the opening stages, despite the surreal atmosphere caused by vast numbers of Blackpool fans continuing to boycott games at Bloomfield Road in protest against controversial owner Owen Oyston.
Willock found the breakthrough and the 19-year-old midfielder's second opportunistic strike in the 37th minute effectively ended the contest.
League One Blackpool continued to press forward gamely but Alex Iwobi completed the scoring eight minutes from time.
Eddie Nketiah wasted two glorious chances inside the opening eight minutes, shooting into the side netting before stretching to prod wide.
Blackpool striker Armand Gnanduillet sashayed around a backpedalling Stephan Lichsteiner to shoot at Petr Cech but the visitors claimed an 11th-minute breakthrough when Aaron Ramsey's deflected free-kick hit the post and fell for Willock to nod in.
There were suspicions of handball against Alex Iwobi when he controlled to combine superbly with Carl Jenkinson, whose low cross was touched on by Nketiah for Willock to finish.
Cech's long punt found Nketiah, only for Mark Howard to save and compound the youngster's frustration.
Lichtsteiner was unable to cut out Marc Bola's 58th-minute cutback but fellow Blackpool full-back Michael Nottingham leant back to lift over.
It was an increasingly lackadaisical showing from Arsenal in the second half and Paudie O'Connor rose unchallenged to head a corner wide.
An injury to Howard brought Blackpool substitute goalkeeper Christoffer Mafoumbi into the fray and he was picking the ball out of the net with 10 minutes to play, although an offside flag denied Willock his hat-trick.
Mafoumbi could only parry Ramsey's shot across goal and the linesman's flag stayed down as Iwobi poached Arsenal's third.
:open_mouth: Oh so close to a hat-trick for @JoeWillock! @seadk6 pulled the ball back for Joe to tap in, but the flag went up against Kolasinac and the goal will not stand— Arsenal FC (@Arsenal) January 5, 2019
What does it mean? More defensive worries for Emery
Although watching some of his young stars and fringe players turn in accomplished showings will have pleased Emery, arguably the most significant moment for the Arsenal boss came before kick-off when Laurent Koscielny pulled up with an apparent back injury. Hopefully a player laid low for most of 2018 by a ruptured Achilles tendon will be back soon.
Koscielny joins Shkodran Mustafi, Hector Bellerin, Nacho Monreal and Rob Holding among the weekend defensive absentees. Although Holding is the only long-term casualty on that list, patching together backlines – this latest assortment did not always convince – is doing Emery few favours on a week-to-week basis.
Willock on the spot for clinical brace
Willock was soon enjoying himself alongside Ramsey, showing plenty of the technical ability in evidence during his Europa League outings. As against Vorskla, he was on the scoresheet and the nature of his goals – timing runs and arriving into the box for simple finishes – bodes well for any attacking midfielder, young or old.
Nketiah fluffs his lines
The Willock role belonged to Nketiah when the latter stunningly announced himself with a cup brace against Norwich City last season. That the 19-year-old has not managed any other goals in a smattering of senior appearances since seemed to weigh upon him as he passed up three clear first-half opportunities.
Arsenal have a clear week to tend to some of their defensive injuries before making the short trip to West Ham in the Premier League, while Blackpool are back in League One action at Portsmouth.