The striker has been in stunning form so far this season, finding the net 22 times in 34 appearances.
Everton tried to do a deal for the Algerian during the January transfer window, but their approach was rebuffed by Sporting.
However, according to O Jogo, the Toffees are now ready to return for Slimani this summer.
Scouts from Merseyside have been watching the 27-year-old in recents weeks and they have returned with glowing reports.
New owner Farhad Moshiri has reportedly provided funds for a summer spending spree and £23m of that will be spent on Slimani.