The #NextGen ATP Australian defeated French veteran Adrian Mannarino 7-6 (4), 6-4 in Sunday's singles final.
De Minaur was nearly flawless on serve, never facing a break point, but squandered 12 chances to go up a break against his French opponent until the final point of the match, when Mannarino netted a backhand.
"I think it's knowing exactly what the other person is going to do at a certain time in the match, trusting each other 100 per cent and knowing that each one of us is willing to work hard 100 per cent every day to get better", said Vliegen.
In the final, the Australian will face Frenchman Adrian Mannarino - a 6-0 4-6 6-1 victor over eighth-seeded Albert Ramos-Vinolas.
"Conditions are really humid here and it was really physical, but I was able to stay really concentrated", the 31-year-old Mannarino said. But the Aussie was more clutch in the big moments, coming through in the first-set tie-break and gaining another 40/0 lead on Mannarino's serve in the final game.
Andreas Seppi of Italy advanced after saving five match points in the deciding tiebreaker before beating local favorite Zhang Zhizhen 7-6 (4), 4-6, 7-6 (8). And the 2019 Next Gen ATP Finals hopeful stayed calm despite seeing break chances come and go.
Carreno Busta won the only previous matchup between the two.