Diogo Jota responded to his omission at the weekend with two goals in a comfortable 5-1 victory as Liverpool got their Carabao Cup defence off to a winning start as 10-man West Ham's difficult start to the season continued.
The Portugal international lost his place to Darwin Nunez for the 3-0 Premier League win over Bournemouth on Saturday, but the two were paired together in a team showing nine changes at Anfield.
Federico Chiesa, on his first start since a summer move from Juventus, showed glimpses of promise in the hour he was afforded, with his mis-hit shot ballooning up off the turf for Jota to pop up in the right place to nod a close-range header past the challenge of goalkeeper Lukasz Fabianski midway through the first half.
That cancelled out Jarell Quansah's own goal from a poorly-defended West Ham corner, but his next strike proved the decisive one.
Four minutes after the interval Curtis Jones carried the ball out of defence, exchanged passes with Cody Gakpo and slid in a pass for Jota to dispatch with a first-time finish.
Having got ahead Slot, whose only concession to youth in his squad was 21-year-old Tyler Morton, turned to the bench and brought on the upgrades of Mohamed Salah and Alexis Mac Allister for Chiesa and Jota.
CARABAO CUP FOURTH-ROUND DRAW
Brentford v Sheffield Wednesday
Southampton v Stoke City
Tottenham Hotspur v Manchester City
AFC Wimbledon/Newcastle United v Chelsea
Manchester United v Leicester City
Brighton v Liverpool
Preston North End v Arsenal
Aston Villa v Crystal Palace
Ties to be played week commencing 28 October
It did not immediately improve things as the visitors, for whom former Reds striker Danny Ings had an 18th-minute goal ruled out for offside, had arguably their best spell with goalkeeper Caoimhin Kelleher denying Michael Antonio, Max Kilman and Aaron Cresswell.
They also had penalty claims waved away Vladimir Coufal's cross hit Kostas Tsimikas in the stomach and then his arm.
But Liverpool's two substitutes combined to score the third which gave them important breathing room as Mac Allister's shot was blocked by Fabianski into the path of Salah who fired home first time.
The Egypt international was then hacked down as he threatened to race clear and Edson Alvarez was sent off for a second bookable offence before Cody Gakpo beat Fabianski at his near post from the edge of the area and then had a shot deflect in off Jean-Clair Toddibo in added time for a quickfire brace.
West Ham, registering seven changes from the weekend, have now lost three of their last four matches to increase the pressure on new head coach Julen Lopetegui.
Ethan Nwaneri scored twice on a historic night for Arsenal after 16-year-old goalkeeper Jack Porter became the club's youngest ever player to start a match in their 5-1 win against Bolton.
Porter, a replacement for the injured David Raya, stole the spotlight ahead of the third-round Carabao Cup fixture at the Emirates Stadium.
But it was the highly-rated Nwaneri whose name was up in lights when he scored a brace either side of the interval on a night to remember for the Enfield 17-year-old.
Declan Rice, Raheem Sterling and Kai Havertz also found the net, with Aaron Collins on target for the League One visitors.
Bolton might be a lowly 19th in League One, but began with confidence and they were demanding a penalty when Josh Sheehan claimed he was bundled over in the box by Gabriel Jesus. Referee Josh Smith waved away their appeals, and less than 60 seconds later, Arsenal were in the lead.
With 16 minutes gone, Arfield fluffed 18-year-old Josh Nichols' rather innocuous looking cross, and Rice was on hand to curl a fine effort past the helpless Luke Southwood.
Nwaneri in just his fourth appearance for the Gunners, and his first start, he soon was celebrating a maiden strike. Another teenager, Myles Lewis-Skelly, 17, found Sterling with a fine through-ball, and the on-loan Chelsea forward's pinpoint cross was mopped up by Nwaneri.
Four minutes into the second half and Nwaneri netted his second. Rice pounced on Chris Forino and Nwaneri, in acres of space, fired underneath Southwood to put Arsenal three clear.
The Gunners were in cruise control but Bolton pulled one back when Collins broke from an Arsenal corner before comfortably rounding Porter and finishing into an empty net with 53 minutes gone.
But 11 minutes later, Arsenal's three-goal advantage was restored. Southwood could only parry surprise starter Bukayo Saka's shot, and Sterling could not miss from a yard out to land his first Arsenal goal on his first start.
Sterling was then involved in Arsenal's fifth, when his shot was saved and substitute Havertz fired home to complete an emphatic victory for the Gunners, who return to their bid for Premier League glory against Leicester at the Emirates on Saturday.
