He was born in Murska Sobota in Vas County of the Kingdom of Hungary (present-day Slovenia), where his father Iván Szlepecz was a blacksmith in the market town; his mother was Julianna Czigány.
[1] Starting in 1896, he served as chaplain for ten years for the Szapáry family, and then in 1906 as the parish priest of Murska Sobota.
Szlepecz initially opposed the autonomy of the Slovene March (Prekmurje) and supported Hungary.
After World War I, he maintained the liturgy in Prekmurje Slovene in St. Nicholas's Church.
Before the First World War, he published articles in Hungarian in Szombathelyi Újság and Muraszombat és vidéke, and articles in Slovene in Marijin list, Novine, and Kalendar Srca Jezušovoga.