Right half-forward Slevin was outstanding, scoring 1-2 from play, 0-7 from frees and 0-1 from a ’65 in difficult conditions.
The game was played in a second half downpour after the sides were level 0-7 apiece at half-time, having been level on seven occasions.
The crucial score arrived in the 38th minute. Daniel Currams made the vital break and when his initial effort for goal was blocked, there was Slevin to crash the ball to the net (1-8 to 0-7).
Rangers played themselves to a standstill but lacked a cutting edge in attack and their cause was totally lost when right full forward Eoin Doyle received a second yellow card in the final quarter.
Scorers for Kilcormac-Killoughey: C Slevin 1-10, 0-7f, 0-1 ’65, J Gorman 0-1.
Scorers for Mt Leinster Rangers: D Murphy 0-5f, E Doyle 0-2, E Coady, R Kelly 0-1 each.
KILCORMAC-KILLOUGHEY: Conor Slevin; J Grogan, G Healion, A McConville; K Grogan, P Healion, B Leonard; D Kilmartin, K Leonard; Ciarán Slevin, C Mahon, P Geraghy; J Gorman, D Currams, T Geraghty.
Subs: T Fletcher for Gorman (inj, 22); J Geraghty for K Leonard (55); M Leonard for P Geraghty (60).
MT LEINSTER RANGERS: F Foley; M Doyle, G Doyle, G Kelly; B Nolan, R Coady, E Coady; R Kelly, D Byrne; J Coady, E Byrne, D Phelan; E Doyle, W Hickey, D Murphy.
Subs: P Coady for J Coady (36); H P O’Byrne for Hickey (51).
Referee: S Cleere (Kilkenny).