A strong effort by Stooke and his colleagues in the pack laid the platform, although England took some time to take full advantage of their superiority.
An early Slade penalty got them off and running, but several other scoring chances were spurned until centreSam Hill exploited a gap in the Italian defence to dot down his first try of the season with 20 played, Slade's conversion put the hosts 10-0 up.
Italian fly half Edoardo Padovani had the chance to reduce the deficit with a penalty, but his kick sailed wide. England punished that miss with their second try just before the break, electric wing Jack Nowell dived over to celebrate his debut with his first Under 20 try to make it 17-0.
It didn't take long for England to penetrate the Italian defence in the second half, scrum half Callum Braley, making his first Under 20 start, burrowed over the line and Slade added the extras to give England a 17-point advantage.
The visitors were reduced to 14-men after 55 minutes and by the 57th minute England were awarded their fourth try by Irish referee Sean Gallagher who blew for a penalty try after heavy dominance from the English scrum. Slade made no mistake with the conversion to make the score 31-0.
Despite being a man down, Italy pushed on and got their first points on the board through replacement Gianmarco Vial who barged his way over the line, but England hit straight back and were awarded their second penalty try of the evening to make the score 38-7 after 65 minutes.
Centre Tom Stephenson, on his home pitch, scored England's sixth try after 70 minutes, showing good strength to force his way over the line, Slade again adding the conversion before Nowell grabbed his second try to round off the scoring.
Despite the 45-point win, Head Coach Rob Hunter says that there is still work to be done:
"It may sound churlish to say that we're unhappy after putting 52 points on the board but the reality is that we know we can play better. Italy were big and they were physical, and to be fair, on a slippery surface they forced us into making mistakes.
"Next week is a big game, and we'll certainly be working very hard over the next few days to make sure we deliver a strong performance against Wales."
Points: Hill 1T, Nowell 2T, Braley 1T, Penalty 2T, Stephenson 1T; Slade 1P, 7C.
England Under 20 side against Italy
15 Ollie Devoto (Bath Rugby)
14 Ben Howard (Worcester Warriors)
13 Mark Jennings (Sale Sharks)
12 Sam Hill (Exeter Chiefs)
11 Jack Nowell (Exeter Chiefs)
10 Henry Slade (Exeter Chiefs)
9 Callum Braley (Bristol Rugby)
1 Danny Hobbs-Awoyemi (Northampton Saints)
2 Luke Cowan-Dickie (Exeter Chiefs)
3 Scott Wilson (Newcastle Falcons)
4 Elliott Stooke (Gloucester Rugby)
5 Dominic Barrow (Leeds Carnegie)
6 Harry Wells (Leicester Tigers)
7 David Sisi (London Irish)
8 Jack Clifford (Harlequins) (c)
16 Nathan Morris (London Wasps) on for Danny Hobbs-Awoyemi 50 mins
17 Alex Lundberg (London Wasps) on for Luke Cowan-Dickie 70 mins
18 Danny Herriott (Northampton Saints) on for Scott Wilson 60 mins
19 Tom Jubb (Saracens) on for Harry Wells 53 mins
20 Gus Jones (London Wasps) on for Gus Jones 75 mins
21 Alex Day (Northampton Saints) on for Callum Braley 60 mins
22 Tom Stephenson (Northampton Saints) on for Sam Hill 44 mins
23 Henry Purdy (Leicester Tigers) on for Ben Howard 70 mins