Here are a few options:
* Haley: This is the most common way to spell the name in Dutch, and it's likely to be understood by most people.
* Hayley: This spelling is also used in Dutch, but it's less common than Haley.
* Heleen: This is a Dutch name that is similar in sound to Hayley, but it has a different meaning.
Ultimately, the best way to spell "Haylee" in Flemish would be to choose the spelling that you find most appealing and that you think is most likely to be understood by the people you're communicating with.