The Three Lions return to Gelsenkirchen on the back of topping Group C with five points to their name, although performances left a lot to be desired.
Southgate particularly struggled to find the perfect partner for Declan Rice, who previously had Kalvin Phillips by his side during England's magical run to the Euro 2020 final.
After trialling Trent Alexander-Arnold and Conor Gallagher in that role, Southgate has given the nod to 19-year-old Kobbie Mainoo, who makes his first major tournament start for his country.
Mainoo's inclusion is the only alteration that Southgate has made to his XI for the last-16 tie, as Phil Foden holds his place on the left despite briefly leaving the camp for the birth of his third child.
Concerns have been raised over Jude Bellingham's fitness, but the Real Madrid man continues in the final third alongside Harry Kane and Bukayo Saka, who holds off Cole Palmer yet again.
John Stones, Jordan Pickford set new England record
Kieran Trippier has also won his race to be fit to continue at left-back, where Luke Shaw is still not fit to start after his muscular injury, although the Manchester United man is on the bench once more.
With John Stones and Jordan Pickford also marshalling the defence, the duo are starting their 23rd straight major tournament game for England, surpassing Ashley Cole for a new joint record.
As for the unfancied Slovakia - who placed third in Group E thanks to a brilliant win over Belgium - head coach Francesco Calzona has gone with an unchanged 4-3-3 for the second game in a row.
David Strelec is again given the green light to start up front over Robert Bozenik, who was named in the first XI in Slovakia's opening two Group E matches, alongside Lukas Haraslin and two-goal Ivan Schranz.
Napoli's Stanislav Lobotka anchors the midfield, where 37-year-old Juraj Kucka will come up against a few familiar faces, having represented Watford in the 2021-22 Premier League campaign.
Paris Saint-Germain's Milan Skriniar and Feyenoord's David Hancko are the standout names in defence, which Martin Dubravka will be barking orders to.
The winner of Sunday's tie will take on Switzerland - who eliminated reigning champions Italy - in the quarter-finals in Dusseldorf on July 6.
England: Pickford; Walker, Stones, Guehi, Trippier; Mainoo, Rice; Saka, Bellingham, Foden; Kane
Subs: Ramsdale, Henderson, Konsa, Gomez, Dunk, Alexander-Arnold, Shaw, Gallagher, Bowen, Toney, Watkins, Eze, Gordon, Palmer, Wharton
Slovakia: Dubravka; Pekarik, Vavro, Skriniar, Hancko; Kucka, Lobotka, Duda; Schranz, Strelec, Haraslin
Subs: Rodak, Ravas, Obert, Rigo, Gyomber, Suslov, Bozenik, Tupta, Benes, Hrosovsky, De Marco, Duris, Bero, Sauer, Kosa