A bogey at the last did not prove costly as Lee finished with a 16-under 272, two strokes ahead of Joost Luiten and Brandon Stone, with Slattery and Levy a shot further back along with Scott Hend.
Lee, who squandered a three-shot lead in the final round of the Maybank Championship Malaysia in February after falling apart down the stretch, said he had managed to keep his nerves in check this time.
"I got a big chance in Malaysia but I didn't make it because I was really, really nervous. Now I made it," he told the Tour's official website.
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"Yesterday I was really, really nervous. We had a lot of break times and then played again so that's really good for me and I just thought about my golf and then competed until I could do it."
Along with a cheque for more than 400,000 euros (311,672.7 pounds), Lee, who was playing the tournament on a sponsor's invitation, also gains a European Tour exemption through the 2018 season.
($1 = 0.8894 euros)
(Reporting by Peter Rutherford; Editing by Andrew Both)
