The 29-year-old made his long-awaited debut against David Wagner’s men, as a second-half substitute for Dwight Gayle.
And despite making a 15-minute cameo, the defender believes his presence paved the way for Ayoze Perez's winner.
“He [Slimani] came on, he was handful and because of his presence in the box, it makes some room for Ayoze’s [goal],” Lascelles told NUFC TV.
The Algeria international who joined the St James' Park outfit on loan during the January transfer window from Leicester City has struggled with a thigh muscle strain injury which kept postponing his maiden appearance for Rafael Benitez's side until Saturday's win against Huddersfield.
The attacker will not take part in their upcoming league encounter when the Magpies travel to the King Power Stadium to take on his parent club on Saturday.