The club said in a statement that Laj will meet his new team with the start of the preparation period for the 2021/22 season next month.
Lagg will succeed fellow countryman Nuno Santo, who quit the club last month.
The Portuguese has spent the last 18 months coaching Benfica.
The 45-year-old took over the Benfica first team in January 2019 and led the Portuguese giants to 18 wins out of 19 and crowned the league title.
And ended a 4-year journey during which Santo, the former coach of Porto, Valencia and Rio Ave, played 198 matches with Wolverhampton, winning 96 of them and losing 56.
Santo worked as a goalkeeper coach in a technical staff led by Josewaldo Ferreira, the former Zamalek coach, in Malaga and Panathinaikos.